CBX1

Chr 17

chromobox 1

Also known as: CBX, HP1-BETA, HP1Hs-beta, HP1Hsbeta, Hp1beta, M31, MOD1, p25beta

NCBI Gene: 10951 ENSG00000108468 UniProt: P83916

This gene encodes a highly conserved nonhistone protein, which is a member of the heterochromatin protein family . The protein is enriched in the heterochromatin and associated with centromeres. The protein has a single N-terminal chromodomain which can bind to histone proteins via methylated lysine residues, and a C-terminal chromo shadow-domain (CSD) which is responsible for the homodimerization and interaction with a number of chromatin-associated nonhistone proteins. The protein may play an important role in the epigenetic control of chromatin structure and gene expression. Several related pseudogenes are located on chromosomes 1, 3, and X. Multiple alternatively spliced variants, encoding the same protein, have been identified. [provided by RefSeq, Jul 2008]

Active trials

Pathogenic / LP

ClinVar variants

Pubs (1 yr)

2.5

Missense Z

0.26

LOEUF· LoF intolerant

Clinical Summary— CBX1

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Population Constraint (gnomAD)

Highly constrained gene — heterozygous loss-of-function variants are very rare in the population (pLI 0.98). One damaged copy is likely sufficient to cause disease.

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ClinVar Variants

9 Pathogenic / Likely Pathogenic· 12 VUS of 21 total submissions

Population Genetics & Constraint

gnomAD v4 — loss-of-function & missense intolerance

gnomAD

LoF intolerant — likely haploinsufficient

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.

0.26LOEUF

pLI 0.976

Z-score 3.14

OE 0.00 (0.00–0.26)

Highly constrained

Highly LoF-intolerant (top ~10% 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.

2.54Z-score

OE missense 0.28 (0.21–0.39)

28 obs / 99.3 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.0.00 (0.00–0.26)

0≤0.351.4

Missense OE?Ratio of observed to expected missense variants. OE ≤ 0.6 = fewer missense variants than expected by chance.0.28 (0.21–0.39)

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.0.81

0≤1.21.6

LoF obs/exp: 0 / 11.5Missense obs/exp: 28 / 99.3Syn Z: 0.91

0.3395th %ile

GOF

0.2497th %ile

LOF

0.70top 10%

The highest-scoring mechanism for this gene is loss-of-function (haploinsufficiency).

LOFprediction above median · LOEUF 0.26

Predictions from Badonyi M, Marsh JA. PLoS ONE. 2024;19(8):e0307312. Mechanism ranking also informed by gnomAD constraint, ClinVar, and ClinGen data.