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Correct splicing despite mutation of the invariant first nucleotide of a 5' splice site: a possible basis for disparate clinical phenotypes in siblings with adenosine deaminase deficiency.

Publication ,  Journal Article
Arredondo-Vega, FX; Santisteban, I; Kelly, S; Schlossman, CM; Umetsu, DT; Hershfield, MS
Published in: Am J Hum Genet
May 1994

Adenosine deaminase (ADA) deficiency usually causes severe combined immune deficiency in infancy. Milder phenotypes, with delayed or late onset and gradual decline in immune function, also occur and are associated with less severely impaired deoxyadenosine (dAdo) catabolism. We have characterized the mutations responsible for ADA deficiency in siblings with striking disparity in clinical phenotype. Erythrocyte dAdo nucleotide pool size, which reflects total residual ADA activity, was lower in the older, more mildly affected sib (RG) than in her younger, more severely affected sister (EG). Cultured T cells, fibroblasts, and B lymphoblasts of RG had detectable residual ADA activity, while cells of EG did not. ADA mRNA was undetectable by northern analysis in these cells of both patients. Both sibs were found to be compound heterozygotes for the following novel splicing defects: (1) a G+1-->A substitution at the 5' splice site of IVS 2 and (2) a complex 17-bp rearrangement of the 3' splice site of IVS 8, which inserted a run of seven purines into the polypyrimidine tract and altered the reading frame of exon 9. PCR-amplified ADA cDNA clones with premature translation stop codons arising from aberrant pre-mRNA splicing were identified, which were consistent with these mutations. However, some cDNA clones from T cells of both patients and from fibroblasts and Epstein-Barr virus (EBV)-transformed B cells of RG, were normally spliced at both the exon 2/3 and exon 8/9 junctions. A normal coding sequence was documented for clones from both sibs. The normal cDNA clones did not appear to arise from either contamination or PCR artifact, and mosaicism seems unlikely to have been involved. These findings suggest (1) that a low level of normal pre-mRNA splicing may occur despite mutation of the invariant first nucleotide of the 5' splice donor sequence and (2) that differences in efficiency of such splicing may account for the difference in residual ADA activity, immune dysfunction, and clinical severity in these siblings.

Duke Scholars

Published In

Am J Hum Genet

ISSN

0002-9297

Publication Date

May 1994

Volume

54

Issue

5

Start / End Page

820 / 830

Location

United States

Related Subject Headings

  • T-Lymphocytes
  • Severe Combined Immunodeficiency
  • RNA, Messenger
  • RNA Splicing
  • Polymerase Chain Reaction
  • Point Mutation
  • Phenotype
  • Nuclear Family
  • Molecular Sequence Data
  • Infant
 

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Arredondo-Vega, F. X., Santisteban, I., Kelly, S., Schlossman, C. M., Umetsu, D. T., & Hershfield, M. S. (1994). Correct splicing despite mutation of the invariant first nucleotide of a 5' splice site: a possible basis for disparate clinical phenotypes in siblings with adenosine deaminase deficiency. Am J Hum Genet, 54(5), 820–830.
Arredondo-Vega, F. X., I. Santisteban, S. Kelly, C. M. Schlossman, D. T. Umetsu, and M. S. Hershfield. “Correct splicing despite mutation of the invariant first nucleotide of a 5' splice site: a possible basis for disparate clinical phenotypes in siblings with adenosine deaminase deficiency.Am J Hum Genet 54, no. 5 (May 1994): 820–30.
Arredondo-Vega FX, Santisteban I, Kelly S, Schlossman CM, Umetsu DT, Hershfield MS. Correct splicing despite mutation of the invariant first nucleotide of a 5' splice site: a possible basis for disparate clinical phenotypes in siblings with adenosine deaminase deficiency. Am J Hum Genet. 1994 May;54(5):820–830.
Journal cover image

Published In

Am J Hum Genet

ISSN

0002-9297

Publication Date

May 1994

Volume

54

Issue

5

Start / End Page

820 / 830

Location

United States

Related Subject Headings

  • T-Lymphocytes
  • Severe Combined Immunodeficiency
  • RNA, Messenger
  • RNA Splicing
  • Polymerase Chain Reaction
  • Point Mutation
  • Phenotype
  • Nuclear Family
  • Molecular Sequence Data
  • Infant