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SPEG
striated muscle enriched protein kinase
SPEG is located on the long (q) arm of chromosome 2, at band 2q35. Arm ratio per GRCh38 - banding schematic.
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Overview
SPEG (striated muscle enriched protein kinase) is located on chromosome 2 and encodes a large serine/threonine kinase predominantly expressed in heart and skeletal muscle. The protein belongs to the myosin light chain kinase family and appears during muscle cell differentiation, suggesting a role in the maturation of contractile structures. Because the gene is selectively enriched in striated muscle, changes affecting SPEG function may disrupt normal muscle development or maintenance, though the full clinical spectrum remains under investigation.
What the gene does
The SPEG protein functions as a kinase, catalysing the transfer of phosphate groups to specific target proteins within muscle cells. This phosphorylation activity is believed to regulate signalling pathways that coordinate the assembly and organisation of contractile filaments during muscle fibre formation. Research suggests the enzyme participates in cytoskeletal remodelling events necessary for establishing the highly ordered sarcomere structure characteristic of striated muscle. By modulating the phosphorylation state of substrate proteins, SPEG may influence cellular processes including differentiation, growth, and the mechanical properties of muscle tissue. The precise molecular targets and downstream signalling networks controlled by SPEG kinase activity continue to be characterised in experimental models.
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Chromosome location
SPEG is situated on the long arm of chromosome 2 at position 2q35. The gene spans a substantial genomic region and produces multiple transcript isoforms through alternative splicing, allowing the generation of protein variants with differing functional properties. The chromosomal band 2q35 contains a number of other genes, some of which also contribute to musculoskeletal biology. Structural features of the SPEG locus and the regulation of its tissue-specific expression pattern remain areas of active study.
Protein structure
Domain architecture has not been experimentally characterised in detail for this protein. The SPEG protein is known to be a large multidomain polypeptide containing kinase catalytic regions typical of the myosin light chain kinase family, but comprehensive mapping of all functional modules and regulatory segments is incomplete. The size and complexity of the protein suggest it may contain additional domains that mediate protein-protein interactions or regulate kinase activity in response to cellular signals.
Key variants
Genetic variants in SPEG include missense changes, nonsense mutations, and small insertions or deletions that may alter protein structure or abundance. Pathogenic variants are thought to impair kinase function or disrupt regulatory mechanisms, potentially interfering with normal muscle development. The clinical significance of many SPEG sequence changes is still being determined, and interpretation often requires assessment of variant frequency, predicted functional impact, and segregation patterns within families.
Sample of pathogenic variants
10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.
| Variant (HGVS) | Protein change | Classification | Evidence | Associated condition |
|---|---|---|---|---|
c.392C>G | p.Ser131Ter | Pathogenic/Likely pathogenic | ★★☆☆ | not provided |
c.1312C>T | p.Gln438Ter | Pathogenic | ★☆☆☆ | not provided |
c.1884_1903dup | p.Ala635fs | Pathogenic | ★☆☆☆ | not provided |
c.331C>T | p.Gln111Ter | Pathogenic | ★☆☆☆ | not provided |
c.3918dup | p.Arg1307fs | Pathogenic | ★☆☆☆ | not provided |
c.4321C>T | p.Gln1441Ter | Pathogenic | ★☆☆☆ | not provided |
c.4350del | p.Ile1451fs | Pathogenic | ★☆☆☆ | not provided |
c.4360_4375del | p.Val1454fs | Pathogenic | ★☆☆☆ | Myopathy, centronuclear, 5 |
c.4645dup | p.Ala1549fs | Pathogenic | ★☆☆☆ | not provided |
c.5407del | p.Arg1803fs | Pathogenic | ★☆☆☆ | not provided |
Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.
Associated conditions
Variants in SPEG have been associated with certain forms of muscle disease, particularly affecting cardiac and skeletal muscle development. Because SPEG is expressed predominantly in striated muscle, pathogenic changes may lead to structural or functional abnormalities in these tissues. The inheritance pattern and penetrance of SPEG-related conditions can vary depending on the nature of the genetic change, and clinical presentations may range in severity. Further research is needed to fully define the phenotypic spectrum and natural history of disorders linked to this gene.
No disease links recorded for this gene in our reference set.
UK clinical status
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
What does the SPEG gene do?
SPEG encodes a protein kinase that is highly expressed in cardiac and skeletal muscle. The enzyme is thought to regulate signalling pathways involved in muscle cell differentiation and the assembly of contractile structures, though its precise molecular targets are still being studied.
How are SPEG variants inherited?
The inheritance pattern for SPEG-related conditions can vary. Some pathogenic variants may follow autosomal recessive inheritance, requiring changes in both gene copies to cause disease, while other scenarios are possible depending on the specific variant and its functional effect.
Are SPEG variants common?
Pathogenic variants in SPEG are rare in the general population. Most sequence changes identified in large-scale databases are benign polymorphisms. Clinically significant SPEG mutations are encountered infrequently and are typically identified through targeted sequencing in individuals with unexplained muscle disease.