Identification of a novel beta-tubulin subfamily with one member (TUBB4Q) located near the telomere of chromosome region 4q35

The human beta-tubulin supergene family consists of several isotypes with m any associated pseudogenes. Here we report the identification of yet anothe r beta-tubulin sequence designated TUBB4Q. This tubulin maps 80 kb proximal to the facioscapulohumeral muscular dystrophy (FSHD1) associated D4Z4 repe ats on chromosome 4q35. The genomic structure contains four exons encoding a putative protein of 434 amino acids. The TUBB4Q nucleotide and protein se quence show 87% and 86% homology to beta 2-tubulin, respectively. Although the genomic structure shows all functional aspects of a genuine gene, no tr anscript could be detected. TUBB4Q-related sequences were identified on mul tiple chromosomes. Since these sequences mutually exhibit a high nucleotide sequence homology, they presumably belong to a novel subfamily of beta-tub ulin genes. Although the chromosome 4q35 tubulin-member probably represents a pseudogene, ectopic expression due to a postulated position effect varie gation (PEV), makes TUBB4Q an ideal dominant-negative candidate gene for FS HD1. Copyright (C) 2000 S. Karger AG, Basel.