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Molecular and structural characterization of five novel mutations in the Bruton's tyrosine kinase gene from patients with X-linked agammaglobulinemia

Saha, BK; Curtis, SK; Vogler, LB and Vihinen, Mauno LU (1997) In Molecular Medicine 3(7). p.477-485
Abstract
Background: The Btk (Bruton's tyrosine kinase) gene has been shown to be mutated in the human immunodeficiency disease, XLA (X-linked agammaglobulinemia). Btk is a member of the Tec family of cytosolic protein tyrosine kinases with distinct functional domains PH, TH, SH3, SH2, and kinase. Mutations have been observed in each of the Btk subdomains in XLA. We have analyzed the Btk gene in six XLA patients from five unrelated families. Materials and Methods: DNA was prepared from the patients' peripheral blood. The Btk exons including the junctional sequences were analyzed by single-strand conformation polymorphism (SSCP) followed by direct nucleotide sequencing after PCR-amplification. For structural analysis, the missense mutations were... (More)
Background: The Btk (Bruton's tyrosine kinase) gene has been shown to be mutated in the human immunodeficiency disease, XLA (X-linked agammaglobulinemia). Btk is a member of the Tec family of cytosolic protein tyrosine kinases with distinct functional domains PH, TH, SH3, SH2, and kinase. Mutations have been observed in each of the Btk subdomains in XLA. We have analyzed the Btk gene in six XLA patients from five unrelated families. Materials and Methods: DNA was prepared from the patients' peripheral blood. The Btk exons including the junctional sequences were analyzed by single-strand conformation polymorphism (SSCP) followed by direct nucleotide sequencing after PCR-amplification. For structural analysis, the missense mutations were introduced into three-dimensional models of the PH and kinase domains of Btk and the outcome was predicted based on the knowledge of the protein function. Results: Five novel mutations and two novel polymorphisms, all of which resulted from single-base alterations, were identified. Three of the five mutations were in the PH domain and two were in the kinase domain of Btk. Three of these mutations were of the missense type, two of which altered the same codon in the PH domain; the third one was located in the kinase domain. The fourth mutation was a point deletion in the PH domain causing a frameshift followed by premature termination. The fifth mutation was a splice donor-site mutation within the kinase domain which could result in an exon skipping. In four of the five instances, mothers of the patients were shown to be obligate carriers. in one instance, a sibling sister was identified as a heterozygote establishing her as a carrier. Conclusions: Functional consequences of the mutations causing frameshifts and altered splicing can be inferred directly. Functional consequences of the missense mutations were interpreted by 3-dimensional structural modeling of Btk domains. It is proposed that the two PH domain mutations will interfere with membrane localization while the kinase domain mutation will interfere with the enzymatic function of Btk. This study provides further insight into the role of Btk in XLA. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
in
Molecular Medicine
volume
3
issue
7
pages
477 - 485
publisher
The Feinstein Institute for Medical Research
external identifiers
  • wos:A1997XN95500007
ISSN
1528-3658
language
English
LU publication?
no
id
719dbe6b-2973-4ee6-a86d-9f2ae18a877d (old id 3852841)
date added to LUP
2013-06-28 14:32:32
date last changed
2016-06-29 09:06:16
@article{719dbe6b-2973-4ee6-a86d-9f2ae18a877d,
  abstract     = {Background: The Btk (Bruton's tyrosine kinase) gene has been shown to be mutated in the human immunodeficiency disease, XLA (X-linked agammaglobulinemia). Btk is a member of the Tec family of cytosolic protein tyrosine kinases with distinct functional domains PH, TH, SH3, SH2, and kinase. Mutations have been observed in each of the Btk subdomains in XLA. We have analyzed the Btk gene in six XLA patients from five unrelated families. Materials and Methods: DNA was prepared from the patients' peripheral blood. The Btk exons including the junctional sequences were analyzed by single-strand conformation polymorphism (SSCP) followed by direct nucleotide sequencing after PCR-amplification. For structural analysis, the missense mutations were introduced into three-dimensional models of the PH and kinase domains of Btk and the outcome was predicted based on the knowledge of the protein function. Results: Five novel mutations and two novel polymorphisms, all of which resulted from single-base alterations, were identified. Three of the five mutations were in the PH domain and two were in the kinase domain of Btk. Three of these mutations were of the missense type, two of which altered the same codon in the PH domain; the third one was located in the kinase domain. The fourth mutation was a point deletion in the PH domain causing a frameshift followed by premature termination. The fifth mutation was a splice donor-site mutation within the kinase domain which could result in an exon skipping. In four of the five instances, mothers of the patients were shown to be obligate carriers. in one instance, a sibling sister was identified as a heterozygote establishing her as a carrier. Conclusions: Functional consequences of the mutations causing frameshifts and altered splicing can be inferred directly. Functional consequences of the missense mutations were interpreted by 3-dimensional structural modeling of Btk domains. It is proposed that the two PH domain mutations will interfere with membrane localization while the kinase domain mutation will interfere with the enzymatic function of Btk. This study provides further insight into the role of Btk in XLA.},
  author       = {Saha, BK and Curtis, SK and Vogler, LB and Vihinen, Mauno},
  issn         = {1528-3658},
  language     = {eng},
  number       = {7},
  pages        = {477--485},
  publisher    = {The Feinstein Institute for Medical Research},
  series       = {Molecular Medicine},
  title        = {Molecular and structural characterization of five novel mutations in the Bruton's tyrosine kinase gene from patients with X-linked agammaglobulinemia},
  volume       = {3},
  year         = {1997},
}