Characterization of the human laminin beta 2 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 beta 2 chain is an important constituent of certain kidney and muscle basement membranes. We have generated a detailed physical map of a 1 10-kb genomic DNA segment surrounding the human laminin beta 2 chain gene ( LAMB2) on chromosome 3p21.3 --> p21.2, a region paralogous with the chromos ome 7q22 --> q31 region that contains the laminin beta 1 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 w as similar to exons 8-12 of the laminin beta 2 chain gene. The LAMB2L-LAMB2 -QARS cluster lies telomeric to the gene encoding the laminin-binding prote in dystroglycan (DAG1).