JAK3

Chr 19AR

Janus kinase 3

Also known as: JAK-3, JAK3_HUMAN, JAKL, L-JAK, LJAK

NCBI Gene: 3718 ENSG00000105639 UniProt: P52333

The protein encoded by this gene is a member of the Janus kinase (JAK) family of tyrosine kinases involved in cytokine receptor-mediated intracellular signal transduction. It is predominantly expressed in immune cells and transduces a signal in response to its activation via tyrosine phosphorylation by interleukin receptors. Mutations in this gene are associated with autosomal SCID (severe combined immunodeficiency disease). [provided by RefSeq, Jul 2008]

Primary Disease Associations & Inheritance

Severe combined immunodeficiency, autosomal recessive, T-negative/B-positive typeMIM #600802

Active trials

Pathogenic / LP

381

ClinVar variants

Pubs (1 yr)

2.8

Missense Z

0.53

LOEUF

Clinical Summary— JAK3

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Gene-Disease Validity (ClinGen)

T-B+ severe combined immunodeficiency due to JAK3 deficiency · ARDefinitive

Definitive — sufficient evidence for diagnostic panels

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Population Constraint (gnomAD)

Low constraint (pLI 0.00) — loss-of-function variants are relatively tolerated in the population.

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ClinVar Variants

41 Pathogenic / Likely Pathogenic· 89 VUS of 381 total submissions

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Clinical Trials

1 active or recruiting trial — potential therapeutic options may be available

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GeneReview available — JAK3

Authoritative clinical overview · Recommended first read

Open GeneReview ↗

Population Genetics & Constraint

gnomAD v4 — loss-of-function & missense intolerance

gnomAD

Moderate LoF intolerance

LoF Constraint?LOEUF (Loss-of-function Observed/Expected Upper bound Fraction) is the upper bound of the 90% CI for LoF OE — the preferred gnomAD v4 metric. Lower = more intolerant to LoF. LOEUF < 0.35 = highly constrained.

0.53LOEUF

pLI 0.000

Z-score 4.34

OE 0.36 (0.25–0.53)

Moderately constrained

More LoF-intolerant than ~75% of genes

Missense Constraint?Missense Z-score: standard deviations fewer missense variants observed vs. expected. Z > 3.09 (p < 0.001) = gene does not tolerate missense variation. OE missense < 0.6 is also considered constrained.

2.81Z-score

OE missense 0.70 (0.65–0.75)

473 obs / 679.2 exp

Mild constraint

Moderately missense-constrained (top ~2.5%)

Observed / Expected Ratios?Shaded band = 90% confidence interval. Vertical tick = point estimate. Grey threshold line = gnomAD constraint cutoff for that variant class.

LoF OE?Ratio of observed to expected LoF variants. Upper CI bound (LOEUF) ≤ 0.35 = strong LoF constraint signal.0.36 (0.25–0.53)

0≤0.351.4

Missense OE?Ratio of observed to expected missense variants. OE ≤ 0.6 = fewer missense variants than expected by chance.0.70 (0.65–0.75)

0≤0.61.4

Synonymous OE?Control metric — synonymous variants are largely neutral and expected near OE = 1.0. Significant deviation may indicate annotation issues.0.84

0≤1.21.6

LoF obs/exp: 19 / 53.1Missense obs/exp: 473 / 679.2Syn Z: 2.18

0.6744th %ile

GOF

0.77top 25%

LOF

0.2679th %ile

This gene has evidence for multiple mechanisms of pathogenicity (gain-of-function and dominant-negative). Both the Badonyi & Marsh prediction and the broader genomic evidence point to gain-of-function as the predominant mechanism. Different variants in this gene may act through different mechanisms — interpret in context of the specific variant.

GOFprediction above median

DNprediction above median

Note: In-silico variant effect predictors (SIFT, PolyPhen, REVEL, CADD) may underestimate pathogenicity of missense variants in genes with GOF or DN mechanisms. Consider functional evidence and clinical context.

Predictions from Badonyi M, Marsh JA. PLoS ONE. 2024;19(8):e0307312.