Genomic Organization of the Mouse β1 Gene: Conservation of the β1D but not of the β1B and β1C Integrin Splice Variants

Abstract

We have determined the genomic organization of the 3′-region of the murine β1 gene and cloned the murine β1D integrin splice variant. Overlapping genomic clones encompassing the region of the β1D-specific exons were isolated from a phage Á FIXII library, mapped and partially sequenced. All of the exon-intron junctions identified in the murine β1 gene fit with the consensus splice donor and acceptor sequences and occur at the same positions as in their human counterparts. cDNA clones for the β1D integrin were isolated from a murine skeletal muscle library. The human and murine β1D sequences are conserved at the nucleotide (93%) and amino acid (100%) level, suggesting an important role of this muscle-specific variant throughout mammalian phylogenesis. In contrast, murine sequences for β1B are very different from human (β1B at both the nucleotide as well as amino acid level. Moreover, no specific polyadenylation signal for the β1B variant could be identified in genomic clones. suggesting that this variant is not present in the mouse. Finally, we were not able to identify a murine β1C splice variant by sequencing analysis. Southern hybridization techniques or polymerase chain reaction of mRN A from platelets. These findings indicate that the β1B and β1C variants emerged relatively late in the phylogenesis of the β1 integrin family.

Key Words:

• Integrin
• Genomic Organization
• Splice Variants