NM_000558.5(HBA1):c.17C>A (p.Ala6Asp) AND none provided

Clinical significance:Uncertain significance (Last evaluated: Jul 24, 2020)

Review status:1 star out of maximum of 4 stars

criteria provided, single submitter

Based on:
1 submission [Details]
Record status:

Allele description [Variation Report for NM_000558.5(HBA1):c.17C>A (p.Ala6Asp)]

NM_000558.5(HBA1):c.17C>A (p.Ala6Asp)

LOC106804613:hemoglobin subunit alpha 1 recombination region [Gene]
HBA1:hemoglobin subunit alpha 1 [Gene - OMIM - HGNC]
Variant type:
single nucleotide variant
Cytogenetic location:
Genomic location:
Preferred name:
NM_000558.5(HBA1):c.17C>A (p.Ala6Asp)
Other names:
  • NC_000016.10:g.176733C>A
  • NG_000006.1:g.37596C>A
  • NG_046166.1:g.2216C>A
  • NG_059186.1:g.5083C>A
  • NM_000558.5:c.17C>AMANE SELECT
  • NP_000549.1:p.Ala6Asp
  • LRG_1225t1:c.17C>A
  • LRG_1225:g.5083C>A
  • LRG_1225p1:p.Ala6Asp
  • NC_000016.9:g.226732C>A
  • P69905:p.Ala6Asp
Protein change:
UniProtKB: P69905#VAR_002721; OMIM: 141800.0078; dbSNP: rs34090856
NCBI 1000 Genomes Browser:
Molecular consequence:
  • NM_000558.5:c.17C>A - missense variant - [Sequence Ontology: SO:0001583]


none provided
MedGen: CN235283

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Assertion and evidence details

Submission AccessionSubmitterReview Status
(Assertion method)
Clinical Significance
(Last evaluated)
SCV001160067ARUP Laboratories, Molecular Genetics and Genomics,ARUP Laboratoriescriteria provided, single submitter
Uncertain significance
(Jul 24, 2020)
germlineclinical testing

Citation Link

Summary from all submissions

EthnicityOriginAffectedIndividualsFamiliesChromosomes testedNumber TestedFamily historyMethod
not providedgermlineunknownnot providednot providednot providednot providednot providedclinical testing

Details of each submission

From ARUP Laboratories, Molecular Genetics and Genomics,ARUP Laboratories, SCV001160067.2

#EthnicityIndividualsChromosomes TestedFamily HistoryMethodCitations
1not providednot providednot providednot providedclinical testingnot provided


The Hb J Toronto variant (HBA1 c.17C>A; p.Ala6Asp, also known as or Ala5Asp when numbered from the mature protein, rs34090856) is reported in the literature in the heterozygous state and in the compound heterozygous state with the 3.7kb deletion in individuals without any significant hematological symptoms (Crookston 1965, Mahdavi 2012, Van Laer 2014). Aberrant HbA1c measurements have been reported in several individuals with this variant (Van Laer 2014). This variant is reported in ClinVar (Variation ID: 15765), and is absent from the general population databases (1000 Genomes Project, Exome Variant Server, Genome Aggregation Database), indicating it is not a common polymorphism. The alanine at codon 6 is weakly conserved, and computational algorithms (SIFT, PolyPhen2) predict that this variant is tolerated. Due to limited information, the clinical significance of this variant is uncertain at this time. References: Crookston J et al. A new haemoglobin, J Toronto (alpha-5 alanine to aspartic acid). Nature. 1965 Dec 11;208(5015):1059-61. Mahdavi M et al. Report of haemoglobin J-Toronto and alpha thalassemia in a family from North of Iran. J Pak Med Assoc. 2012 Apr;62(4):396-8. Van Laer C et al. Aberrant glycated haemoglobin (HbA1c) results leading to haemoglobinopathy diagnosis in four Belgian patients. Acta Clin Belg. 2014 Dec;69(6):456-9.

OriginAffectedNumber testedTissuePurposeMethodIndividualsAllele frequencyFamiliesCo-occurrences
1germlineunknownnot providednot providednot providednot providednot providednot providednot provided

Last Updated: Jan 25, 2021

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