rs1128827
Variant summary
Our verdict is Uncertain significance. Variant got 0 ACMG points: 2P and 2B. PM2BP4_Moderate
The NR_002174.2(CMAHP):n.1141G>T variant causes a non coding transcript exon change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a benign outcome for this variant. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.
Frequency
Genomes: not found (cov: 32)
Exomes 𝑓: 0.0 ( 0 hom. )
Failed GnomAD Quality Control
Consequence
CMAHP
NR_002174.2 non_coding_transcript_exon
NR_002174.2 non_coding_transcript_exon
Scores
1
1
Clinical Significance
Not reported in ClinVar
Conservation
PhyloP100: 3.17
Genes affected
CMAHP (HGNC:2098): (cytidine monophospho-N-acetylneuraminic acid hydroxylase, pseudogene) Sialic acids are terminal components of the carbohydrate chains of glycoconjugates involved in ligand-receptor, cell-cell, and cell-pathogen interactions. The two most common forms of sialic acid found in mammalian cells are N-acetylneuraminic acid (Neu5Ac) and its hydroxylated derivative, N-glycolylneuraminic acid (Neu5Gc). Studies of sialic acid distribution show that Neu5Gc is not detectable in normal human tissues although it was an abundant sialic acid in other mammals. Neu5Gc is, in actuality, immunogenic in humans. The absense of Neu5Gc in humans is due to a deletion within the human gene CMAH encoding cytidine monophosphate-N-acetylneuraminic acid hydroxylase, an enzyme responsible for Neu5Gc biosynthesis. Sequences encoding the mouse, pig, and chimpanzee hydroxylase enzymes were obtained by cDNA cloning and found to be highly homologous. However, the homologous human cDNA differs from these cDNAs by a 92-bp deletion in the 5' region. This deletion, corresponding to exon 6 of the mouse hydroxylase gene, causes a frameshift mutation and premature termination of the polypeptide chain in human. It seems unlikely that the truncated human hydroxylase mRNA encodes for an active enzyme explaining why Neu5Gc is undetectable in normal human tissues. Human genomic DNA also shows evidence of this deletion which does not occur in the genomes of African great apes. Nonetheless, the CMAH gene maps to 6p21.32 in humans and great apes indicating that mutation of the CMAH gene occurred following human divergence from chimpanzees and bonobos. [provided by RefSeq, Jul 2008]
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ACMG classification
Classification made for transcript
Verdict is Uncertain_significance. Variant got 0 ACMG points.
PM2
?
Very rare variant in population databases, with high coverage;
BP4
?
Computational evidence support a benign effect (BayesDel_noAF=-0.36).
Transcripts
RefSeq
Gene | Transcript | HGVSc | HGVSp | Effect | #exon/exons | MANE | UniProt |
---|---|---|---|---|---|---|---|
CMAHP | NR_002174.2 | n.1141G>T | non_coding_transcript_exon_variant | 8/13 |
Ensembl
Gene | Transcript | HGVSc | HGVSp | Effect | #exon/exons | TSL | MANE | Appris | UniProt |
---|---|---|---|---|---|---|---|---|---|
CMAHP | ENST00000377993.8 | n.1149G>T | non_coding_transcript_exon_variant | 9/14 | 1 | ||||
ENST00000643807.1 | n.1505G>T | non_coding_transcript_exon_variant | 11/16 | ||||||
ENST00000648291.1 | n.392+18359C>A | intron_variant, non_coding_transcript_variant |
Frequencies
GnomAD3 genomes ? Cov.: 32
GnomAD3 genomes
?
Cov.:
32
GnomAD4 exome Data not reliable, filtered out with message: AC0 AF: 0.00 AC: 0AN: 315980Hom.: 0 Cov.: 0 AF XY: 0.00 AC XY: 0AN XY: 178600
GnomAD4 exome
Data not reliable, filtered out with message: AC0
AF:
AC:
0
AN:
315980
Hom.:
Cov.:
0
AF XY:
AC XY:
0
AN XY:
178600
Gnomad4 AFR exome
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GnomAD4 genome ? Cov.: 32
GnomAD4 genome
?
Cov.:
32
ClinVar
Not reported inComputational scores
Source:
Name
Calibrated prediction
Score
Prediction
BayesDel_noAF
Benign
CADD
Benign
DANN
Uncertain
Splicing
Find out detailed SpliceAI scores and Pangolin per-transcript scores at