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Gene

MMAB

metabolism of cobalamin associated B

Summary

Cytogenetic location
12q24.11
Coordinates
Chromosome 12: 109,553,715–109,573,504 (GRCh38)
Exons
9 exons across 19.8 kb
Protein
250 amino acids
Also known as
cblB, CFAP23
MANE Select transcript
ENST00000545712.7NM_052845.4
Locus type
Protein-coding
  • Very high
  • Confident
  • Low
  • Very low

Curated reports relevant to this gene

  • Homocystinuria & Cobalamin Disorders

    • Inborn Disorders of Cobalamin Metabolism and TransportAutosomal recessive

      Includes defects in vitamin B12 absorption and transport such as Imerslund-Gräsbeck syndrome (CUBN, AMN), intrinsic factor deficiency (CBLIF) and transcobalamin II deficiency (TCN2), as well as intracellular cobalamin processing defects, which can cause megaloblastic anaemia, nerve damage and failure to thrive.

      • ClinGen rates the link definitive
      • 6 GenCC submitters rate it definitive or strong
      Actionability

      Knowing allows lifelong vitamin B12 injections or other cobalamin treatment, which can prevent anaemia and neurological damage.

  • Methylmalonic & Propionic Acidemia

    • Methylmalonic AcidemiaAutosomal recessive

      Caused by variants in MMUT, MMAA, MMAB, MCEE and related cobalamin-processing genes, which can cause vomiting, poor feeding, metabolic crises, developmental problems and kidney disease.

      • ClinGen rates the link definitive
      • 6 GenCC submitters rate it definitive or strong
      Actionability

      Knowing allows specialist dietary management, carnitine, vitamin B12 for responsive forms and an emergency plan, which reduces the risk of crises.

How MMAB is laid out

  • Coding sequence
  • Untranslated region
  • Intron
  • Direction of transcription
  • Known disease-causing sites
Chromosome 12, with a bracket where MMAB sits. MMAB and 16 genes near it on chromosome 12, from 109,063,610 to 110,063,609.Chromosome 1212q24.11p13.33p13.32p13.31p13.2p13.1p12.3p12.2p12.1p11.23p11.22p11.21p11.1q11q12q13.11q13.12q13.13q13.2q13.3q14.1q14.2q14.3q15q21.1q21.2q21.31q21.32q21.33q22q23.1q23.2q23.3q24.11q24.12q24.13q24.21q24.22q24.23q24.31q24.32q24.33109.2 Mb109.4 Mb109.6 Mb109.8 Mb110 MbUSP30: 109,023,089–109,088,023, forward strandUSP30ALKBH2: 109,085,154–109,098,462, reverse strandALKBH2UNG: 109,097,569–109,126,725, forward strandUNGACACB: 109,116,320–109,268,226, forward strandACACBFOXN4: 109,277,978–109,309,289, reverse strandFOXN4MYO1H: 109,347,900–109,455,523, forward strandMYO1HKCTD10: 109,448,655–109,477,359, reverse strandKCTD10UBE3B: 109,477,375–109,536,705, forward strandUBE3BMMAB: 109,553,715–109,573,504, reverse strandMMABMVK: 109,573,255–109,600,609, forward strandMVKFAM222A: 109,713,819–109,770,495, forward strandFAM222ATRPV4: 109,783,087–109,833,542, reverse strandTRPV4GLTP: 109,850,943–109,880,549, reverse strandGLTPTCHP: 109,900,264–109,983,841, forward strandTCHPGIT2: 109,929,792–109,996,389, reverse strandGIT2ANKRD13A: 109,999,186–110,039,763, forward strandANKRD13AC12orf76: 110,020,353–110,073,636, reverse strandC12orf76Diagram of MMAB: 9 exons on the reverse strand of chromosome 12Exon 9: 6 known disease-causing sitesExon 8: 5 known disease-causing sitesExon 7: 20 known disease-causing sitesExon 6: 7 known disease-causing sitesExon 5: 3 known disease-causing sitesExon 4: 2 known disease-causing sitesExon 3: 7 known disease-causing sitesExon 2: 2 known disease-causing sitesExon 1: 11 known disease-causing sitesExon 9: 109,553,715–109,557,136, 3,422 basesExon 8: 109,559,096–109,559,155, 60 basesExon 7: 109,561,040–109,561,104, 65 basesExon 6: 109,561,420–109,561,517, 98 basesExon 5: 109,561,780–109,561,852, 73 basesExon 4: 109,565,119–109,565,176, 58 basesExon 3: 109,568,770–109,568,863, 94 basesExon 2: 109,571,649–109,571,710, 62 basesExon 1: 109,573,347–109,573,504, 158 bases9876543215′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 4.1 kb of the gene's 19.8 kb; 753 of those bases code for the protein.

Sequencing MMAB

1Low

How hard MMAB is to sequence with short reads, out of 100

  • Mappability0%
  • Homology0%
  • Repeats5.4%
  • GC content5.5%
  • Reference coverage0%

80

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

None of them falls in a region short reads find hard.

A whole genome covers all 19.8 kb of MMAB, introns included, not only the 4.1 kb of exons.

Genes linked to the same conditions

Traits linked to MMAB

The Human Phenotype Ontology lists these as features of the rare conditions MMAB can cause. Each trait's page lists the other genes linked to it.

External links

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 2026-10-17: 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 Genome in a Bottle genome stratifications, from NIST: the sequencing difficulty score.
  • The Human Phenotype Ontology, release 2026-09-01: the traits linked to the gene. Find out more at hpo.jax.org.
  • Data release 2026.10.18-e609d43e.

Cite this page

APA

Dante Labs. (n.d.). MMAB gene: metabolism of cobalamin associated B. Retrieved 18 October 2026, from https://dantelabs.com/genes/mmab

Vancouver

Dante Labs. MMAB gene: metabolism of cobalamin associated B [Internet]. [cited 18 October 2026]. Available from: https://dantelabs.com/genes/mmab

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