Molecular characterization of a t(2;6) balanced translocation that is associated with a complex phenotype and leads to truncation of the TCBA1 gene.

The molecular characterization of balanced chromosomal rearrangements has often been a powerful tool for the positional identification of genes associated with specific diseases. In some instances, these rearrangements may be associated with a variety of different phenotypes, and thus establishing a genotype-phenotype correlation may be a complex process. However, molecular characterization of the rearrangement remains a useful tool for diagnoses or prognoses, or for identifying new genes and establishing a gene-to-function relationship. In this work we describe the characterization of a de novo balanced translocation t(2;6)(q24.3;q22.31) found in a patient with a complex phenotype. The major clinical finding was a severe neurological involvement. Thanks to the molecular characterization of this translocation we found that the rearrangement led to the truncation of the TCBA1 gene on chromosome 6q. We found that the gene is transcribed in different splice variants and is highly specific for the central nervous system. TCBA1 does not show any similarity with other known genes, and no information is available about its function. However, the gene appears to be well conserved among species, and we were able to infer the sequence of a putative mouse homolog of TCBA1. This allowed us to perform a more detailed expression study in mice, thus confirming its specificity for the nervous system. This finding is of particular interest because it suggests that TCBA1 may be correlated with the neurological phenotype of our patient, and possibly mutated in genetic diseases with a neurological phenotype. Copyright 2005 Wiley-Liss, Inc.