Journal Article

Aberrant splicing induced by missense mutations in <i>BRCA1</i>: clues from a humanized mouse model

Yongping Yang, Srividya Swaminathan, Betty K. Martin and Shyam K. Sharan

in Human Molecular Genetics

Volume 12, issue 17, pages 2121-2131
Published in print September 2003 | ISSN: 0964-6906
Published online September 2003 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/ddg222
Aberrant splicing induced by missense mutations in BRCA1: clues from a humanized mouse model

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Numerous missense mutations in human BRCA1 gene have been linked to predisposition to breast cancer. However, the functional significance of the majority of these mutations remains unknown. We have examined the molecular basis for three such cancer-causing mutations. The first mutation, a T→G transversion in codon 64, is predicted to change a conserved cysteine residue to glycine in the RING finger domain of the 1863 amino acid BRCA1 protein. Using a humanized mouse model we demonstrate that this missense mutation actually results in a functionally null protein. This striking result occurs because the single base alteration generates a new 5′ splice site in exon 5 and also disrupts a putative exonic splicing enhancer motif. Consequently, the normal splice donor site is disrupted and an internal cryptic splice site is activated. This results in a 22-nucleotide deletion and the aberrant transcript is predicted to encode a severely truncated protein consisting of only 63 amino acids. To identify other missense mutations in BRCA1 that may result in aberrant splicing, we screened various mutations using the Genscan program. We demonstrate that at least two other missense mutations in codons 1495 and 1823 result in aberrant splicing due to the possible disruption of cis-acting splicing regulatory elements. In conclusion, our study demonstrates for the first time the application of a humanized mouse model for functional analysis of human mutations in mice and also shows the need for a careful examination of the functional consequences of single base alterations and single nucleotide polymorphisms identified in human disease-causing genes.

Journal Article.  7565 words.  Illustrated.

Subjects: Genetics and Genomics

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