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Gene

MMAA

metabolism of cobalamin associated A

Summary

Cytogenetic location
4q31.21
Coordinates
Chromosome 4: 145,619,385–145,660,033 (GRCh38)
Exons
7 exons across 40.6 kb
Protein
418 amino acids
Inheritance
Autosomal recessive
Also known as
cblA
MANE Select transcript
ENST00000649156.2NM_172250.3
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 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
      • 7 GenCC submitters rate it definitive or strong
      What knowing changes

      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
      • 7 GenCC submitters rate it definitive or strong
      What knowing changes

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

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 MMAA is laid out

  • Coding sequence
  • Untranslated region
  • Intron
  • Direction of transcription
  • Known disease-causing sites
  • Stretches short reads find hard
Chromosome 4, with a bracket where MMAA sits. MMAA and 4 genes near it on chromosome 4, from 145,139,709 to 146,139,708.Chromosome 44q31.21p16.3p16.2p16.1p15.33p15.32p15.31p15.2p15.1p14p13p12p11q11q12q13.1q13.2q13.3q21.1q21.21q21.22q21.23q21.3q22.1q22.2q22.3q23q24q25q26q27q28.1q28.2q28.3q31.1q31.21q31.22q31.23q31.3q32.1q32.2q32.3q33q34.1q34.2q34.3q35.1q35.2145.2 Mb145.4 Mb145.6 Mb145.8 Mb146 MbOTUD4: 145,110,838–145,180,631, reverse strandOTUD4SMAD1: 145,480,769–145,559,191, forward strandSMAD1MMAA: 145,619,385–145,660,033, forward strandMMAAC4orf51: 145,680,088–145,771,032, forward strandC4orf51ZNF827: 145,757,627–145,939,036, reverse strandZNF827Diagram of MMAA: 7 exons on the forward strand of chromosome 4Exon 2: 41 known disease-causing sitesExon 3: 19 known disease-causing sitesExon 4: 20 known disease-causing sitesExon 5: 9 known disease-causing sitesExon 6: 11 known disease-causing sitesExon 7: 22 known disease-causing sitesExon 1: 145,619,385–145,619,407, 23 basesExon 2: 145,639,075–145,639,578, 504 basesExon 3: 145,642,363–145,642,485, 123 basesExon 4: 145,645,986–145,646,156, 171 basesExon 5: 145,651,062–145,651,147, 86 basesExon 6: 145,653,994–145,654,143, 150 basesExon 7: 145,655,147–145,660,033, 4,887 bases12345675′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 5.9 kb of the gene's 40.6 kb; 1,257 of those bases code for the protein.

How a genome test reads MMAA

131

positions in MMAA 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 40.6 kb of MMAA, introns included, not only the 5.9 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.). MMAA gene: metabolism of cobalamin associated A. Retrieved 16 October 2026, from https://dantelabs.com/genes/mmaa

Vancouver

Dante Labs. MMAA gene: metabolism of cobalamin associated A [Internet]. [cited 16 October 2026]. Available from: https://dantelabs.com/genes/mmaa

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