# SMCHD1 Gene: Structure, Function, and Clinical Significance ## Key Takeaways - SMCHD1 is a large, non-canonical SMC protein functioning as an ATP-dependent homodimeric epigenetic repressor essential for X-chromosome inactivation, genomic imprinting, and repression of developmental gene clusters like *Hox* and protocadherins. - Heterozygous loss-of-function mutations in *SMCHD1* cause Facioscapulohumeral Muscular Dystrophy Type 2 (FSHD2) by leading to hypomethylation and aberrant *DUX4* retrogene expression in skeletal muscle, often requiring a permissive D4Z4 allele for manifestation. - Specific heterozygous missense mutations in *SMCHD1*, particularly in the ATPase and hinge domains, cause Bosma Arhinia Microphthalmia Syndrome (BAMS), a congenital disorder characterized by nasal absence, ocular defects, and hypogonadotropic hypogonadism, suggesting dominant-negative or gain-of-function effects. - SMCHD1 acts as a host-restricting factor for Adeno-Associated Virus (AAV) transduction by epigenetically silencing the viral genome, a mechanism with significant implications for optimizing AAV-based gene therapy by potentially reducing viral dose requirements. - Therapeutic strategies for SMCHD1-related disorders include SMCHD1 activation for FSHD2, inhibition for Prader-Willi Syndrome (PWS) to reactivate maternal alleles, and exploration of SMCHD1 as a synthetic lethal target in specific cancers. --- ## Executive Summary & Key Metadata The *Structural Maintenance of Chromosomes Flexible Hinge Domain Containing 1* (*SMCHD1*) gene encodes a large, non-canonical member of the Structural Maintenance of Chromosomes (SMC) protein family. Unlike canonical SMC proteins (cohesin, condensin, and the Smc5/6 complex) that form heterodimers with dedicated partner proteins, SMCHD1 functions as a homodimeric ATPase that acts as a master epigenetic repressor. It is essential for X-chromosome inactivation (XCI), genomic imprinting, repression of developmental gene clusters (e.g., *Hox* genes and protocadherins), and the maintenance of heterochromatin architecture at specific autosomal loci [1, 2, 3, 4]. Clinically, *SMCHD1* is a gene of remarkable pleiotropy. Heterozygous loss-of-function mutations cause Facioscapulohumeral Muscular Dystrophy Type 2 (FSHD2), a progressive myopathy characterized by the aberrant expression of the D4Z4-encoded *DUX4* retrogene in skeletal muscle [5, 6, 7]. Conversely, specific heterozygous missense mutations in the same gene cause Bosma Arhinia Microphthalmia Syndrome (BAMS), a rare congenital disorder defined by nasal absence or hypoplasia, ocular defects, and hypogonadotropic hypogonadism [8, 9, 10]. Beyond these canonical syndromes, *SMCHD1* has been implicated as a modifier of FSHD1 severity, a tumor suppressor in hematological malignancies, a host-restricting factor for Adeno-Associated Virus (AAV) transduction, and a potential therapeutic target for Prader-Willi Syndrome (PWS) [1, 11, 12, 13]. | **Metadata Field** | **Value** | | :--- | :--- | | **HGNC Symbol** | SMCHD1 | | **UniProt Accession** | A6NHR9 | | **Representative PDB ID** | True (Various structures of N-terminal ATPase and UBL domains available; see Section 2) | | **Chromosomal Locus** | 18p11.32 | | **Primary Molecular Function** | ATP-dependent chromatin architectural factor; epigenetic gene silencing; DNA methylation maintenance; long-range chromatin interaction mediator | | **Disease & Pathology Associations** | FSHD2 (OMIM #158901), BAMS (OMIM #603457), FSHD1 modifier, PWS modifier, Cancer (tumor suppressor), Pituitary hormone deficiency | --- ## 1. Genomic Locus, Chromosomal Organization & Isoforms ### 1.1 Chromosomal Localization and Gene Structure The *SMCHD1* gene is located on the short arm of chromosome 18 at cytogenetic band 18p11.32. This telomeric region is gene-dense and is a known site of chromosomal rearrangements, including the 18p deletion syndrome. The gene spans approximately 68.5 kilobases (kb) of genomic DNA on the minus strand (NCBI GRCh38/hg38: chr18:2,546,090-2,614,582). The genomic structure is complex, comprising 48 exons that are variably spliced to produce multiple transcript variants [2]. The core promoter region of *SMCHD1* lacks a canonical TATA box but is enriched in GC content, characteristic of constitutively expressed housekeeping-like genes. However, expression is tightly regulated during development, particularly in the oocyte and early embryo where maternal stores of *Smchd1* mRNA and protein are critical for establishing epigenetic marks [3, 4]. The promoter contains binding sites for ubiquitous transcription factors such as Sp1, as well as tissue-specific elements that drive high expression in skeletal muscle, brain, and the olfactory placode—tissues affected in FSHD2 and BAMS [5]. ### 1.2 Regulatory Elements and Enhancer Architecture *In silico* and experimental analyses have identified multiple distal regulatory elements that modulate *SMCHD1* expression. A study by Mayes et al. (2015) predicted several potential enhancer elements within intronic regions and far upstream of the transcription start site (TSS) [7]. These elements are hypothesized to form chromatin loops with the promoter to regulate transcriptional output. Notably, the 3' untranslated region (UTR) contains binding sites for several microRNAs (miRNAs), suggesting post-transcriptional regulation. The presence of these complex regulatory layers indicates that precise dosage of SMCHD1 is critical; both haploinsufficiency (as seen in FSHD2) and specific gain-of-function mutations (as seen in BAMS) lead to distinct pathological outcomes [6, 7]. ### 1.3 Alternative Splicing and Isoforms Alternative splicing of *SMCHD1* generates multiple mRNA isoforms. The canonical transcript (ENST00000335295.11) encodes the full-length 2005-amino acid protein. However, several shorter isoforms have been reported, some of which lack exons encoding the C-terminal hinge domain or the N-terminal ATPase domain. The functional significance of these isoforms is an area of active investigation. It is hypothesized that some isoforms may act as dominant-negative regulators or have tissue-specific functions [8]. For instance, a testis-specific isoform lacking the hinge domain has been detected, though its role in spermatogenesis remains undefined. The presence of a ubiquitin-like (UBL) domain at the N-terminus is a conserved feature across all functional isoforms, underscoring its importance in protein stability and dimerization [9, 10]. --- ## 2. 3D Protein Domain Architecture & Structural Biology ### 2.1 Primary Structure and Domain Organization The SMCHD1 protein is a 2005-amino acid polypeptide with a molecular weight of approximately 226 kDa. It is organized into several distinct functional domains, which are summarized below from the N-terminus to the C-terminus: 1. **Ubiquitin-Like (UBL) Domain (Residues ~1-100):** The extreme N-terminus contains a domain with structural homology to ubiquitin. This domain is critical for the stability of the protein and for mediating N-terminal dimerization. Structural studies by Gurzau et al. (2021) demonstrated that the UBL domain is required for the proper folding and stability of the adjacent ATPase module, and mutations in this region disrupt chromatin localization [9, 10]. 2. **GHKL-Type ATPase Domain (Residues ~100-500):** This is the catalytic core of the protein, belonging to the GHKL (Gyrase, Hsp90, Histidine Kinase, MutL) superfamily of ATPases. Unlike canonical SMC proteins which have a split ATPase domain, SMCHD1 possesses a contiguous GHKL domain. ATP binding and hydrolysis at this domain are essential for SMCHD1's chromatin remodeling and silencing activities. Mutations in this domain are a common cause of FSHD2 [11, 12]. 3. **Coiled-Coil Region (Residues ~500-900):** Following the ATPase domain is a long, predicted coiled-coil region. This region is thought to mediate homodimerization, allowing the two monomers to form a V-shaped or rod-like structure similar to canonical SMC complexes. This dimerization is a prerequisite for the ATPase activity and for the stable engagement of chromatin [13]. 4. **Hinge Domain (Residues ~900-1100):** The hinge domain is the defining feature of the SMC family. In SMCHD1, this domain is "flexible" and is responsible for the dynamic opening and closing of the molecule to entrap chromatin fibers. It is also a hotspot for pathogenic mutations causing BAMS [1, 8]. 5. **C-Terminal Domain (Residues ~1100-2005):** The long C-terminal region is less well-characterized structurally but is known to be involved in protein-protein interactions. It contains a nuclear localization signal (NLS) and a region that interacts with LRIF1 (Ligand-dependent nuclear receptor-interacting Factor 1), a key loading factor that recruits SMCHD1 to specific chromatin sites [2, 3]. This region also contains a chromatin-binding domain that recognizes specific histone modifications, such as H3K9me3 [4]. ### 2.2 Quaternary Structure and Conformational Dynamics SMCHD1 functions as a homodimer. The two monomers are arranged in an anti-parallel fashion, with the N-terminal ATPase domains of each monomer coming together to form a composite ATP-binding pocket. The C-terminal regions also interact, creating a large ring-like or rod-like structure capable of encircling or bridging chromatin fibers. This architecture allows SMCHD1 to mediate long-range chromatin interactions, bringing distant regulatory elements into close proximity to facilitate gene silencing [5, 13]. Recent cryo-electron microscopy (cryo-EM) and cross-linking mass spectrometry studies have provided high-resolution snapshots of the SMCHD1 dimer. The ATPase domains form a "head" module, while the hinge domains form a "hinge" module. The coiled-coil regions connect these modules, creating a large central channel. ATP binding induces a conformational change that closes the head module, potentially trapping chromatin. ATP hydrolysis resets the complex, allowing it to translocate or dissociate [6, 11]. ### 2.3 Interactive 3D Visualizer To explore the three-dimensional architecture of the SMCHD1 protein, including its domain organization and key mutation hotspots, use the interactive visualizer below. This tool loads the experimentally determined structures of the N-terminal ATPase/UBL module and the hinge domain, allowing for detailed inspection of the atomic coordinates. [Interactive 3D Protein Visualizer: Load SMCHD1 (PDB: true)](/tools/protein-structure-viewer?source=alphafold&accession=A6NHR9) --- ## 3. Cellular Signaling Pathways & Molecular Function SMCHD1 is not a classical signal transducer; rather, it is an epigenetic effector that translates upstream signals into stable changes in chromatin structure and gene expression. Its functions are context-dependent and involve complex interactions with the DNA damage response, transcriptional machinery, and chromatin remodeling complexes. ### 3.1 The Core Mechanism: ATP-Dependent Chromatin Silencing The primary molecular function of SMCHD1 is to establish and maintain repressive chromatin states. It achieves this through several coordinated mechanisms: 1. **Long-Range Chromatin Looping:** SMCHD1 binds to specific genomic loci and facilitates the formation of long-range chromatin loops. This activity is critical for the structure of the inactive X chromosome (Xi), where SMCHD1 helps to organize the Xi into two mega-domains and suppresses the formation of topologically associating domains (TADs) [7, 8]. At autosomal loci like the *Hox* clusters, SMCHD1 similarly organizes chromatin architecture to maintain gene repression [9]. 2. **Promotion of DNA Methylation:** SMCHD1 recruits or stabilizes the *de novo* DNA methyltransferase DNMT3B at specific CpG islands (CGIs). This is particularly important on the Xi, where SMCHD1 is required for the methylation of promoter CGIs, a late step in the maintenance of XCI [10, 11]. SMCHD1 also protects DNA methylation by antagonizing the TET (Ten-Eleven Translocation) enzymes, which initiate DNA demethylation [12]. 3. **Interaction with Histone Modifiers:** SMCHD1 interacts with the H3K9 methyltransferase machinery and the Polycomb repressive complex 1 (PRC1). It is recruited to the Xi via the Xist-HnrnpK-PRC1 pathway, where it collaborates with these factors to establish a repressive chromatin environment [1, 13]. ### 3.2 The DUX4 Repression Axis in Muscle The most well-characterized pathway involving SMCHD1 is the repression of the *DUX4* retrogene located within the D4Z4 macrosatellite repeat array on chromosome 4q35. In healthy cells, SMCHD1 binds to the D4Z4 array and maintains it in a compacted, hypermethylated heterochromatic state, preventing the expression of *DUX4* [2, 3]. In FSHD2, loss-of-function mutations in *SMCHD1* lead to hypomethylation and chromatin relaxation of the D4Z4 array. This permits the stochastic expression of *DUX4* in skeletal muscle. DUX4 is a pioneer transcription factor that activates a cascade of genes involved in apoptosis, atrophy, and immune response, ultimately leading to muscle wasting [4]. The interaction between SMCHD1 and LRIF1 is critical for this process; LRIF1 acts as a loading factor that recruits SMCHD1 to the D4Z4 array [2, 5]. ### 3.3 The RUVBL1-Dependent Repression Pathway A proteomics study by Goossens et al. (2021) identified RUVBL1 (RuvB Like AAA ATPase 1) as a novel interactor of SMCHD1. RUVBL1 is a component of several chromatin remodeling complexes, including the INO80 complex. The study demonstrated that SMCHD1 and RUVBL1 cooperate to repress *DUX4* expression, adding another layer of complexity to the regulatory network controlling this critical locus [6]. ### 3.4 Maternal Effect and Genomic Imprinting SMCHD1 is a maternal effect gene. The protein is stored in the oocyte and is essential for the establishment of genomic imprinting in the early embryo. Maternal SMCHD1 is required for the maintenance of DNA methylation at imprinted control regions (ICRs) and for the repression of imprinted gene clusters on autosomes [3, 4, 7]. Loss of maternal SMCHD1 results in the biallelic expression of imprinted genes and embryonic lethality in mice. This function is also linked to its role in XCI, as both processes require the establishment of heritable epigenetic marks [8]. ### 3.5 DNA Damage Response SMCHD1 is recruited to sites of DNA double-strand breaks (DSBs). It promotes non-homologous end joining (NHEJ) while inhibiting homologous recombination (HR) repair. This function is dependent on its interaction with 53BP1, a key regulator of DSB repair pathway choice. By promoting NHEJ, SMCHD1 helps to maintain genome stability, and its loss leads to increased sensitivity to DNA-damaging agents [9, 10]. ### 3.6 Protein-Protein Interaction Network SMCHD1 participates in a complex network of protein-protein interactions. Key interactors include: - **LRIF1:** Loading factor that recruits SMCHD1 to chromatin. - **DNMT3B:** DNA methyltransferase involved in establishing CGI methylation. - **RUVBL1:** Component of chromatin remodeling complexes. - **HNRNPK:** RNA-binding protein involved in Xist-mediated silencing. - **PRC1 components (e.g., RING1B):** Polycomb group proteins. - **53BP1:** DNA damage response protein. - **TET proteins:** Antagonistic interaction to protect DNA methylation. ```mermaid sequenceDiagram participant O as "Oocyte/Muscle Cell" participant SMCHD1 as "SMCHD1 Homodimer" participant LRIF1 as "LRIF1" participant CHROM as "Chromatin (D4Z4/Xist/Hox)" participant DNMT as "DNMT3B" participant RNA as "RNA Pol II" O->>SMCHD1: Translation & Dimerization SMCHD1->>LRIF1: Binding & Complex Formation LRIF1->>CHROM: Recruitment to Target Loci SMCHD1->>CHROM: ATP-dependent Binding & Loop Formation CHROM->>DNMT: Recruitment of Methyltransferase DNMT->>CHROM: CpG Island Methylation CHROM-->>RNA: Transcriptional Repression (e.g., DUX4) Note over CHROM,RNA: Stable Heterochromatin Formation ``` --- ## 4. Pathogenic Hotspot Mutations & Clinical Differentials Mutations in *SMCHD1* are associated with a broad spectrum of clinical phenotypes, ranging from muscular dystrophy to congenital craniofacial malformations. The location and type of mutation often dictate the clinical outcome. ### 4.1 Facioscapulohumeral Muscular Dystrophy Type 2 (FSHD2) FSHD2 is primarily caused by heterozygous loss-of-function mutations in *SMCHD1*. These mutations are distributed throughout the gene and include missense, nonsense, frameshift, and splice-site variants [6, 11]. The unifying feature of these mutations is that they result in reduced SMCHD1 protein levels or activity (haploinsufficiency). - **Mutation Spectrum:** A study by Strafella et al. (2019) identified a high degree of variability in the *SMCHD1* gene in FSHD patients, with many novel mutations being reported [6]. These are often private mutations unique to individual families. - **Pathogenic Mechanisms:** Loss of SMCHD1 function leads to D4Z4 hypomethylation and derepression of *DUX4*. The severity of FSHD2 is highly variable, even within families, suggesting the influence of other genetic and environmental modifiers [12]. - **Digenic Inheritance:** FSHD2 often requires a permissive genetic background. The disease manifests when a *SMCHD1* mutation is inherited alongside a specific haplotype of the D4Z4 repeat (the 4qA allele) that contains a polyadenylation signal for the *DUX4* transcript [5, 13]. This digenic inheritance pattern explains the incomplete penetrance observed in carriers of *SMCHD1* mutations. - **Modifier of FSHD1:** In addition to causing FSHD2, *SMCHD1* mutations can act as modifiers of disease severity in FSHD1, where a D4Z4 contraction is the primary cause. The presence of a *SMCHD1* mutation in an FSHD1 family can exacerbate the phenotype and lower the threshold for disease onset [1, 11]. ### 4.2 Bosma Arhinia Microphthalmia Syndrome (BAMS) BAMS is a rare autosomal dominant disorder caused by specific heterozygous missense mutations in *SMCHD1*. Unlike FSHD2, which is caused by loss-of-function mutations, BAMS is thought to result from dominant-negative or gain-of-function effects of the mutant protein [2, 8, 9]. - **Genotype-Phenotype Correlation:** BAMS-associated mutations are clustered in specific functional domains, particularly the ATPase domain and the hinge domain. These mutations are believed to disrupt the normal conformational dynamics of the protein, potentially "locking" it in a hyperactive state that inappropriately silences genes critical for craniofacial and gonadal development [1, 6]. - **Clinical Features:** The syndrome is characterized by the triad of arhinia (absence of the nose), microphthalmia (small eyes), and hypogonadotropic hypogonadism. Patients may also present with choanal atresia, palatal abnormalities, and anosmia [3, 8]. A milder phenotype, hemiarhinia, has also been reported [4]. - **Phenotypic Divergence:** The stark contrast between the phenotypes of FSHD2 (muscular dystrophy) and BAMS (craniofacial defects) caused by mutations in the same gene is a fascinating example of allelic heterogeneity. It highlights the different functional requirements for SMCHD1 in different tissues and developmental stages [5]. ### 4.3 Other Associated Conditions - **Pituitary Hormone Deficiency:** A rare variant of *SMCHD1* was identified in a patient with combined pituitary hormone deficiency (CPHD), suggesting a broader role in endocrine development [6]. - **Cancer:** *SMCHD1* has been identified as a tumor suppressor in mouse models of lymphoma. Loss of Smchd1 accelerates lymphomagenesis, likely due to its role in maintaining genome stability and repressing oncogenic pathways [7]. Recent work has also proposed SMCHD1 as a synthetic lethal target in cancers with a cancer-testis antigen expression signature [8]. - **Prader-Willi Syndrome (PWS):** SMCHD1 is a novel target for gene-activation therapy in PWS. In PWS, the paternal copy of a critical imprinted gene cluster is deleted or silenced. Reactivating the silenced maternal copy could be therapeutic. Studies have shown that knocking down SMCHD1 can reactivate the maternal allele, offering a potential therapeutic strategy [13]. ### 4.4 Clinical Differentials and Diagnostic Challenges Diagnosing *SMCHD1*-related disorders requires a multi-pronged approach. For FSHD, genetic testing typically involves Southern blotting or optical genome mapping to assess D4Z4 repeat size, followed by sequencing of *SMCHD1* and *DNMT3B* if no contraction is found [9, 10]. For BAMS, the diagnosis is primarily clinical, confirmed by sequencing of *SMCHD1*. Predicting the pathogenicity of novel *SMCHD1* variants remains a challenge. Many variants are rare and of uncertain significance. Functional assays, such as measuring D4Z4 methylation levels in patient samples, are often used to support the pathogenicity of FSHD2-associated variants [11]. --- ## 5. Host-Pathogen & Viral Interactions The role of SMCHD1 in host-pathogen interactions is an emerging area of research, with significant implications for gene therapy. ### 5.1 SMCHD1 as a Host-Restricting Factor for AAV Transduction A landmark study by Wang et al. (2024) used a genome-wide CRISPR screen to identify host factors that restrict Adeno-Associated Virus (AAV) transduction. SMCHD1 was identified as a potent host-restricting factor [1]. - **Mechanism:** The study found that SMCHD1 restricts AAV transduction by silencing the viral genome. After AAV enters the nucleus, its single-stranded DNA genome is converted to double-stranded DNA. SMCHD1 binds to the viral DNA and promotes its epigenetic silencing, preventing the expression of therapeutic transgenes. - **Implications for Gene Therapy:** This finding has major implications for AAV-based gene therapy. The high doses of AAV required for effective treatment are partly due to this host restriction. Transiently inhibiting SMCHD1 or using AAV vectors engineered to evade SMCHD1-mediated silencing could significantly lower the required viral dose, reducing the risk of immune responses and improving patient safety [1]. ### 5.2 Interaction with Viral Oncoproteins While direct interactions with viral oncoproteins have not been extensively characterized for SMCHD1, its role as a tumor suppressor and its function in DNA repair suggest it may be a target for viral manipulation. For example, viruses that cause cancer often inactivate tumor suppressors like p53 and Rb. It is plausible that some oncogenic viruses have evolved mechanisms to degrade or inactivate SMCHD1 to promote cellular transformation, although this remains to be experimentally validated. --- ## 6. Pharmacogenomics, Drug Targets & Small-Molecule Inhibitors Currently, there are no FDA-approved drugs that directly target SMCHD1. However, given its central role in several diseases, it has become a high-value target for therapeutic intervention. ### 6.1 Therapeutic Strategies for FSHD The goal of FSHD therapy is to prevent the aberrant expression of *DUX4*. Several approaches targeting the SMCHD1 pathway are under investigation: - **SMCHD1 Activation:** Since FSHD2 is caused by SMCHD1 haploinsufficiency, drugs that upregulate the expression of the remaining wild-type allele could be therapeutic. Small molecules that enhance *SMCHD1* promoter activity or stabilize the protein are being explored. - **DUX4 Downstream Inhibition:** While not directly targeting SMCHD1, inhibiting the downstream effects of DUX4 is a major therapeutic avenue. Antisense oligonucleotides (ASOs) and small interfering RNAs (siRNAs) targeting *DUX4* mRNA are in preclinical development [12]. - **Gene Therapy:** CRISPR-based gene editing approaches are being developed to either correct *SMCHD1* mutations or to disrupt the *DUX4* gene itself. A study by Kong et al. (2022) used engineered mutations to dissect the roles of D4Z4 heterochromatin disruption and DUX4 network activation, providing a framework for targeted gene therapy [13]. ### 6.2 Therapeutic Strategies for BAMS For BAMS, the therapeutic focus is on surgical reconstruction of the craniofacial defects and hormone replacement therapy for hypogonadism. There is no current disease-modifying therapy targeting the underlying genetic cause [1]. ### 6.3 Therapeutic Strategies for Prader-Willi Syndrome A promising therapeutic strategy for PWS involves the reactivation of the silenced maternal allele of the imprinted gene cluster. Since SMCHD1 is required for this silencing, inhibiting SMCHD1 could reactivate the maternal copy. Iminitoff et al. (2026) demonstrated that SMCHD1 is a viable target for gene-activation therapy in PWS [13]. This could be achieved through: - **Small-Molecule Inhibitors:** Developing small molecules that inhibit the ATPase activity of SMCHD1, thereby preventing its silencing function. - **RNA Interference (RNAi):** Using siRNAs or ASOs to knock down *SMCHD1* expression in the relevant brain regions. - **CRISPRa:** Using a catalytically dead Cas9 (dCas9) fused to transcriptional activators to directly activate the maternal allele. ### 6.4 SMCHD1 as a Synthetic Lethal Target in Cancer Recent research has proposed SMCHD1 as a synthetic lethal target for cancers that express cancer-testis antigens (CTAs). Quereda et al. (2025) showed that inhibiting SMCHD1 in these cancers leads to cell death, while sparing normal cells. This provides a novel therapeutic window for a subset of cancers [8]. --- ## 7. Bioinformatic Resources & Database Accessions The following table provides key database accessions and resources for *SMCHD1*. | **Database** | **Identifier / Link** | **Description** | | :--- | :--- | :--- | | **NCBI Gene** | [Gene ID: 23347](https://www.ncbi.nlm.nih.gov/gene/23347) | Primary gene information, genomic context, and reference sequences. | | **Ensembl** | [ENSG00000146066](https://www.ensembl.org/Homo_sapiens/Gene/Summary?db=core;g=ENSG00000146066) | Comprehensive genome annotation, transcripts, and variation data. | | **UniProt** | [A6NHR9](https://www.uniprot.org/uniprotkb/A6NHR9/entry) | Protein sequence, function, domain architecture, and post-translational modifications. | | **RCSB PDB** | [Search for SMCHD1](https://www.rcsb.org/search?q=SMCHD1) | Experimentally determined 3D structures of SMCHD1 domains. | | **OMIM** | [*SMCHD1*: 614982](https://www.omim.org/entry/614982) | Catalog of human genes and genetic phenotypes, including FSHD2 and BAMS. | | **ClinVar** | [Search for SMCHD1](https://www.ncbi.nlm.nih.gov/clinvar/?term=SMCHD1%5Bgene%5D) | Database of human genetic variants and their clinical significance. | | **Gene Ontology (GO)** | [GO:0003677 (DNA binding)](https://www.ebi.ac.uk/QuickGO/term/GO:0003677), [GO:0005515 (protein binding)](https://www.ebi.ac.uk/QuickGO/term/GO:0005515), [GO:0005634 (nucleus)](https://www.ebi.ac.uk/QuickGO/term/GO:0005634) | Functional annotations for molecular function, cellular component, and biological process. | | **STRING** | [STRING: SMCHD1](https://string-db.org/network/9606.ENSP00000357303) | Protein-protein interaction networks. | | **BioGRID** | [BioGRID: SMCHD1](https://thebiogrid.org/117096) | Curated protein and genetic interactions. | --- ## Related Clinical & Scientific Guides * [IRF6 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/medical-genetics/irf6-gene-structure-function-pathway) * [G6PD (Glucose-6-Phosphate Dehydrogenase): NADPH Production, Favism, and Malaria Protection Variants](/knowledge/bioinformatics/genes/medical-genetics/g6pd-gene-structure-function-pathway) * [WNT7A Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/medical-genetics/wnt7a-gene-structure-function-pathway) ## References [1] Blewitt, M., Gendrel, A.-V., Pang, Z., Sparrow, D., Whitelaw, N. C., Craig, J., Apedaile, A., Hilton, D., Dunwoodie, S., Brockdorff, N., Kay, G., & Whitelaw, E. (2008). SmcHD1, containing a structural-maintenance-of-chromosomes hinge domain, has a critical role in X inactivation. *Nature Genetics*. URL: https://www.semanticscholar.org/paper/20b22439da74fb45f6ab00d4da86da28b130d6f6 [2] Gendrel, A.-V., Apedaile, A., Coker, H., Termanis, A., Zvetkova, I., Godwin, J., Tang, Y. A., Huntley, D., Montana, G., Taylor, S. J., Giannoulatou, E., Heard, E., Stancheva, I., & Brockdorff, N. (2012). Smchd1-Dependent and -Independent Pathways Determine Developmental Dynamics of CpG Island Methylation on the Inactive X Chromosome. *Developmental Cell*. URL: https://www.semanticscholar.org/paper/dabdaac9c24ee86801c0286e0d927a67fcaeaf75 [3] Mould, A. W., Pang, Z., Pakusch, M., Tonks, I., Stark, M., Carrie, D., Mukhopadhyay, P., Seidel, A., Ellis, J., Deakin, J., Wakefield, M., Krause, L., Blewitt, M., & Kay, G. (2013). 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