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SHOC2
SHOC2 leucine rich repeat scaffold protein
SHOC2 encodes a leucine-rich-repeat scaffold protein that assembles a phosphatase complex activating RAF1 in the RAS/MAPK cascade. A recurrent heterozygous gain-of-function SHOC2 variant (p.Ser2Gly) causes autosomal dominant Noonan syndrome with loose anagen hair, a distinctive RASopathy subtype with thin sparse hair, hyperactive behaviour, short stature and cardiac involvement.
SHOC2 is located on the long (q) arm of chromosome 10, at band 10q25.2. Arm ratio per GRCh38 - banding schematic.
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Overview
SHOC2 (SHOC2 leucine rich repeat scaffold protein) is located on chromosome 10 at position 10q25.2 and encodes a 582-amino acid protein that serves as a critical molecular scaffold in cellular signalling networks. The SHOC2 protein functions within the RAS-MAPK pathway, one of the most fundamental signalling cascades in human biology, by bringing together key enzymes and regulatory molecules to ensure appropriate signal transmission from the cell surface to the nucleus.
Pathogenic variants in SHOC2 follow an autosomal dominant inheritance pattern, meaning a single altered copy of the gene is sufficient to cause clinical features. These variants typically result in abnormal activation of the RAS-MAPK pathway, leading to a condition classified within the RASopathy spectrum - a group of related developmental disorders caused by dysregulated signalling through this critical pathway. The gene has been recognised in multiple UK clinical genomics panels, reflecting its established role in developmental anomalies and cardiovascular disorders. Cancer predisposition associated with germline SHOC2 variants is an area of ongoing research, with surveillance considerations based on the gene's pathway role rather than established risk figures.
What the gene does
The SHOC2 protein operates as a molecular scaffold that coordinates protein-protein interactions essential for RAS-MAPK signal transduction. This pathway relays signals from growth factors and other extracellular stimuli, ultimately controlling gene expression patterns that determine whether cells divide, differentiate, or undergo programmed death. SHOC2 specifically facilitates the formation of a complex that includes RAF kinases and protein phosphatase 1C (PP1c), modulating the phosphorylation state and activity of pathway components.
The protein's leucine-rich repeat structure creates a curved scaffold surface capable of binding multiple partners simultaneously, positioning it as a signal integration hub. SHOC2 enhances the efficiency of RAF activation downstream of RAS, effectively amplifying growth signals when appropriate stimuli are present. The regulatory mechanism involves dynamic assembly and disassembly of protein complexes, with SHOC2 recruitment to the plasma membrane occurring in response to upstream signals. This spatial and temporal control ensures that growth-promoting signals are transmitted with proper intensity and duration.
The interaction between SHOC2 and PP1c through the RVxF motif represents a key regulatory node, as dephosphorylation events controlled by this phosphatase influence RAF kinase activity. Disruption of SHOC2 function affects the balance between kinase and phosphatase activities within the pathway, leading to altered downstream signalling that manifests as developmental and proliferative abnormalities across multiple organ systems.
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Chromosome location
SHOC2 is positioned on the long arm of chromosome 10 at cytogenetic band 10q25.2, a region that has been mapped in detail through genome sequencing efforts. The gene occupies a defined chromosomal territory that places it among other genes involved in cellular signalling and metabolic regulation. Structural variations affecting this chromosomal region, though rare, can potentially influence SHOC2 expression or function through positional effects or copy number changes.
Protein structure
The SHOC2 protein exhibits a modular architecture dominated by leucine-rich repeat (LRR) motifs that form the functional core of the molecule. The N-terminal region comprises a disordered segment spanning amino acids 1-88, which provides regulatory flexibility and may participate in protein-protein interactions that are context-dependent. Embedded within this disordered region is the RVxF motif at amino acids 63-66, a short sequence critical for interaction with PP1c phosphatase.
The central and C-terminal portions of SHOC2 contain 13 leucine-rich repeats (LRR 1 through LRR 13), beginning at amino acid 101 and extending to position 400. These repeats, each approximately 20-24 amino acids in length, stack together to create a curved solenoid structure characteristic of LRR-containing proteins. This architecture generates a concave surface ideal for protein binding, allowing SHOC2 to function as a scaffold that brings together multiple signalling molecules simultaneously. The repeating leucine residues at regular intervals stabilise the three-dimensional fold through hydrophobic packing, while variable residues on the exposed surface provide specificity for partner recognition. This domain organisation enables SHOC2 to serve as both a structural platform and a regulatory node within the RAS-MAPK signalling network.
Key variants
Pathogenic variants in SHOC2 predominantly affect the gene's regulatory function within the RAS-MAPK pathway, with the majority of clinically significant changes resulting in pathway overactivation rather than simple loss of function. The variant landscape includes both germline alterations associated with developmental RASopathies and, more rarely, somatic changes identified in tumour samples. Most constitutional pathogenic variants exhibit a gain-of-function effect, enhancing RAF activation and amplifying downstream signalling beyond physiological levels.
A well-documented recurrent variant (written as c.4A>G in genetic test reports, indicating a DNA change at position 4) affecting the gene's normal splicing pattern has been particularly well characterised, leading to aberrant mRNA processing that produces a protein with altered regulatory properties. Missense variants affecting leucine-rich repeat domains can disrupt normal protein-protein interactions, either enhancing or reducing SHOC2's ability to coordinate signalling complexes. The functional consequences of individual variants depend on their precise location within the protein structure and their impact on key interaction surfaces.
Sample of pathogenic variants
6 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.4A>G | p.Ser2Gly | Pathogenic | ★★★☆ | Noonan syndrome-like disorder with loose anagen hair 1 |
c.519G>A | p.Met173Ile | Pathogenic | ★★★☆ | RASopathy |
c.519G>C | p.Met173Ile | Pathogenic | ★★☆☆ | RASopathy |
c.807_808delinsTT | p.Gln269_His270delinsHisTyr | Pathogenic | - | Noonan syndrome-like disorder with loose anagen hair 1 |
c.157G>A | p.Gly53Arg | Likely pathogenic | ★☆☆☆ | Noonan syndrome-like disorder with loose anagen hair 1 |
c.520C>T | p.Leu174Phe | Likely pathogenic | - | Noonan syndrome |
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
Pathogenic variants in SHOC2 cause a specific RASopathy characterised by features overlapping with Noonan syndrome but distinguished by the presence of loose anagen hair, a distinctive finding in affected individuals. This condition, sometimes termed Noonan-like syndrome with loose anagen hair (also known as Noonan syndrome with loose anagen hair, or NSLAH), presents with short stature, characteristic facial features including widely spaced eyes and low-set ears, cardiovascular abnormalities (particularly pulmonary valve stenosis and hypertrophic cardiomyopathy), and developmental delays of varying severity.
The loose anagen hair, from which the condition derives part of its name, refers to hair that can be pulled out easily without pain due to reduced anchoring within hair follicles. Additional features may include skin pigmentation changes, lymphatic abnormalities, and mild intellectual disability. The cancer predisposition associated with SHOC2 variants reflects the gene's role in growth regulation, though the absolute risk elevation and tumour spectrum remain areas of ongoing research as more individuals with molecularly confirmed variants are identified and followed longitudinally.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic SHOC2 variants typically follow autosomal dominant inheritance.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
UK clinical status
SHOC2 has been classified with green (high evidence) status across numerous NHS Genomic Medicine Service gene panels (curated lists of genes tested for specific clinical indications), reflecting robust evidence for its clinical validity. The gene appears on the RASopathies panel, where it is recognised as a definitive cause of Noonan-like syndrome with loose anagen hair. Its inclusion on both adult and childhood solid tumour cancer susceptibility panels acknowledges the emerging understanding of cancer predisposition associated with RASopathy genes.
Additional panel memberships include Intellectual disability, Monogenic short stature, and Paediatric or syndromic cardiomyopathy, reflecting the multi-system nature of SHOC2-related conditions. The gene also features on panels for Fetal anomalies, Fetal hydrops, Primary lymphoedema, and Pigmentary skin disorders, demonstrating the diverse clinical presentations that may prompt genetic testing. This broad panel representation ensures that individuals presenting with various combinations of developmental, cardiac, or growth features may be offered appropriate genomic testing that includes SHOC2 analysis.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Diet & lifestyle considerations
Research into lifestyle modifications specific to individuals with SHOC2 variants remains limited, as the condition is relatively rare and management focuses primarily on addressing individual clinical features rather than gene-specific interventions. General population studies suggest that maintaining cardiovascular health through appropriate physical activity may benefit individuals with cardiac abnormalities, though exercise recommendations should be individualised based on the specific cardiac lesions present and guided by cardiology assessment.
Nutritional support may be relevant for children with growth delays or feeding difficulties, with some families reporting benefit from working with dietitians experienced in growth disorders. Early intervention services addressing developmental delays have shown general benefit in RASopathy populations, though outcomes vary considerably between individuals. Families often find value in connecting with support organisations focused on RASopathies, which provide information-sharing opportunities and psychosocial support, though such resources should complement rather than replace clinical care.
Supplement considerations
No supplements have been conclusively shown to prevent or modify the progression of SHOC2-related conditions. While some families consider nutritional supplementation to support growth in children with short stature, there is no robust evidence that any specific supplement alters final adult height or other core features of the condition. Growth hormone therapy, sometimes considered under specialist endocrinology supervision for select individuals with short stature, represents a medical intervention distinct from supplementation and requires careful monitoring and individualised assessment.
Before considering any supplement, individuals should discuss potential benefits and risks with their healthcare team, as some compounds may interact with medications used to manage cardiac or other features of the condition. The focus of clinical management remains on evidence-based interventions targeting specific complications rather than preventive supplementation.
Frequently asked questions
What does the SHOC2 gene do?
SHOC2 provides instructions for making a scaffold protein that helps regulate the RAS-MAPK signalling pathway, a critical cellular communication system controlling growth, development, and cell division. The protein brings together key signalling molecules, ensuring that growth signals are transmitted appropriately from the cell surface to the nucleus.
How are SHOC2 variants inherited?
SHOC2 variants follow an autosomal dominant pattern, meaning a pathogenic change in one of the two gene copies is sufficient to cause clinical features. An affected individual has a 50% chance of passing the variant to each child, though most cases arise from new (de novo) variants not present in either parent.
What is loose anagen hair in SHOC2-related conditions?
Loose anagen hair refers to scalp hair that can be removed easily and painlessly because it is not firmly anchored in hair follicles. This distinctive feature, often present from early childhood, helps distinguish SHOC2-related RASopathy from other conditions in this spectrum and reflects the gene's role in cellular adhesion processes affecting hair follicles.
Are heart problems common with SHOC2 variants?
Cardiovascular abnormalities occur frequently in individuals with pathogenic SHOC2 variants, with pulmonary valve stenosis and hypertrophic cardiomyopathy among the most commonly reported features. The specific cardiac findings vary between individuals, and regular cardiology monitoring is typically recommended to detect and manage any abnormalities that develop.
Why is SHOC2 included on cancer susceptibility panels?
SHOC2 appears on cancer susceptibility panels because the RAS-MAPK pathway it regulates is fundamental to controlling cell division, and dysregulation of this pathway can contribute to tumour development. While the precise cancer risks associated with germline SHOC2 variants continue to be defined as more data accumulates, its pathway role justifies surveillance consideration in clinical genomics programmes.