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Gene

CBS

cystathionine beta-synthase

Summary

Cytogenetic location
21q22.3
Coordinates
Chromosome 21: 43,053,191–43,075,835 (GRCh38)
Exons
17 exons across 22.6 kb
Protein
551 amino acids
Inheritance
Autosomal recessive
Also known as
HIP4
MANE Select transcript
ENST00000398165.8NM_000071.3
Locus type
gene with protein product
  • Very high
  • Confident
  • Low
  • Very low

Reference genomeGRCh38

Positions on gene and variant pages follow this choice, in this browser.

Curated report relevant to this gene

  • Homocystinuria & Cobalamin Disorders

    • HomocystinuriaAutosomal recessive

      Includes classic homocystinuria due to CBS deficiency, severe MTHFR deficiency and the combined and remethylation cobalamin disorders, which can cause lens dislocation, blood clots, skeletal changes, anaemia and developmental problems.

      • ClinGen rates the link definitive
      • 6 GenCC submitters rate it definitive or strong
      What knowing changes

      Knowing allows treatment with vitamin B6, B12, folate, betaine and diet as appropriate, which can prevent lens dislocation, thrombosis and other complications.

Inheritance

Autosomal recessive
It takes a changed copy from each parent. With one, you are a carrier and usually unaffected; when both parents are carriers, each child has a one-in-four chance of inheriting two.

How CBS is laid out

  • Coding sequence
  • Untranslated region
  • Intron
  • Direction of transcription
  • Known disease-causing sites
  • Stretches short reads find hard
Chromosome 21, with a bracket where CBS sits. CBS and 10 genes near it on chromosome 21, from 42,564,513 to 43,564,512.Chromosome 2121q22.3p13p12p11.2p11.1q11.1q11.2q21.1q21.2q21.3q22.11q22.12q22.13q22.2q22.342.6 Mb42.8 Mb43 Mb43.2 Mb43.4 MbSLC37A1: 42,495,994–42,581,440, forward strandSLC37A1PDE9A: 42,653,584–42,776,512, forward strandPDE9AWDR4: 42,843,013–42,879,583, reverse strandWDR4NDUFV3: 42,879,644–42,913,304, forward strandNDUFV3ERVH48-1: 42,916,803–42,925,630, reverse strandERVH48-1PKNOX1: 42,974,328–43,034,494, forward strandPKNOX1CBS: 43,053,191–43,075,835, reverse strandCBSU2AF1: 43,092,956–43,107,605, reverse strandU2AF1CRYAA: 43,169,008–43,172,810, forward strandCRYAASIK1: 43,414,483–43,427,137, reverse strandSIK1HSF2BP: 43,529,186–43,659,524, reverse strandHSF2BPDiagram of CBS: 17 exons on the reverse strand of chromosome 21Exon 17: 5 known disease-causing sitesExon 15: 4 known disease-causing sitesExon 14: 14 known disease-causing sitesExon 13: 9 known disease-causing sitesExon 12: 11 known disease-causing sitesExon 11: 10 known disease-causing sitesExon 10: 16 known disease-causing sitesExon 9: 11 known disease-causing sitesExon 8: 14 known disease-causing sitesExon 7: 10 known disease-causing sitesExon 6: 11 known disease-causing sitesExon 5: 20 known disease-causing sitesExon 4: 6 known disease-causing sitesExon 3: 11 known disease-causing sitesExon 17: 43,053,191–43,053,983, 793 basesExon 16: 43,056,803–43,056,887, 85 basesExon 15: 43,058,145–43,058,253, 109 basesExon 14: 43,058,834–43,058,968, 135 basesExon 13: 43,059,226–43,059,303, 78 basesExon 12: 43,060,441–43,060,546, 106 basesExon 11: 43,062,311–43,062,395, 85 basesExon 10: 43,062,953–43,063,078, 126 basesExon 9: 43,063,900–43,063,991, 92 basesExon 8: 43,065,203–43,065,272, 70 basesExon 7: 43,065,387–43,065,521, 135 basesExon 6: 43,065,616–43,065,695, 80 basesExon 5: 43,066,243–43,066,377, 135 basesExon 4: 43,068,509–43,068,615, 107 basesExon 3: 43,071,985–43,072,201, 217 basesExon 2: 43,073,266–43,073,341, 76 basesExon 1: 43,075,770–43,075,835, 66 bases1716141210864215′3′

Exons of the gene's MANE Select transcript (release v1.5), from NCBI and EMBL-EBI, on the GRCh38 reference genome.

Chromosome bands from UCSC's GRCh38 ideogram (2022-10-29).

Nearby genes from Ensembl release 116, on GRCh38.

Exons make up 2.5 kb of the gene's 22.6 kb; 1,656 of those bases code for the protein.

How a genome test reads CBS

179

positions in CBS where ClinVar classes a change as pathogenic or likely pathogenic

179 of them (100%) fall in regions short reads find hard.

  • Low mappability (179 sites)Regions where 100 bp or 250 bp reads cannot be placed uniquely.
  • Segmental duplications (179 sites)Copies of at least 1 kb sharing at least 90% identity with another part of the genome (paralogues, pseudogenes); reads may align to the wrong copy.

A whole genome covers all 22.6 kb of CBS, introns included, not only the 2.5 kb of exons.

Where this comes from

  • HGNC: the gene's symbol, name, other symbols and location.
  • MANE Select v1.5, from NCBI and EMBL-EBI: the transcript, its exons and coding sequence.
  • GenCC and ClinGen, released 2026-10-16: which conditions the gene is linked to, and how strongly.
  • The ACMG secondary findings list, SF v3.2.
  • ClinVar and the GIAB stratifications: known disease-causing sites, and the regions short reads find hard.
  • The Human Phenotype Ontology, release 2026-09-01: the traits linked to the gene. Find out more at hpo.jax.org.
  • Data release 2026.10.16-c6eea6bf.

Cite this page

APA

Dante Labs. (n.d.). CBS gene: cystathionine beta-synthase. Retrieved 16 October 2026, from https://dantelabs.com/genes/cbs

Vancouver

Dante Labs. CBS gene: cystathionine beta-synthase [Internet]. [cited 16 October 2026]. Available from: https://dantelabs.com/genes/cbs

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