Characterization of the human laminin β2 chain locus (LAMB2): linkage to a gene containing a nonprocessed, transcribed LAMB2-like pseudogene (LAMB2L) and to the gene encoding glutaminyl tRNA synthetase (QARS)

The laminin β2 chain is an important constituent of certain kidney and muscle basement membranes. We have generated a detailed physical map of a 110-kb genomic DNA segment surrounding the human laminin β2 chain gene (LAMB2) on chromosome 3p21.3→p21.2, a region paralogous with the chromosome 7q22→q31 region that contains the laminin β1 chain gene locus (LAMB1). Several CpG islands and a novel polymorphic microsatellite marker (D3S4594) were identified. The 3′ end of LAMB2 lies 16 kb from the 5′ end of the glutaminyl tRNA synthetase gene (QARS). About 20 kb upstream of LAMB2 we found a gene encoding a transcribed, non-processed LAMB2-like pseudogene (LAMB2L). The sequence of 1.75 kb of genomic DNA at the 3′ end of LAMB2L was similar to exons 8–12 of the laminin β2 chain gene. The LAMB2L–LAMB2–QARS cluster lies telomeric to the gene encoding the laminin-binding protein dystroglycan (DAG1).