BACKGROUND:Several studies have suggested that chromosome 19q13.1-3 contains asthma susceptibility genes. OBJECTIVE:Linkage and association analyses using 587 United Kingdom and Dutch asthma families (n = 2819 subjects) were used to investigate this region. METHODS:A 3-phase procedure was used: (1) linkage and association analyses using 15 microsatellite markers spanning 14.4 mega base pairs (Mbps) on 19q13, (2) fine mapping of the refined region using 26 haplotype tagging single nucleotide polymorphisms (SNPs), and (3) dense gene analyses using 18 SNPs evaluated for association with asthma, bronchial hyperresponsiveness (BHR), FEV1, plasma urokinase plasminogen activator receptor (PLAUR), and rate of annual FEV1 decline in subjects with asthma. RESULTS:The microsatellite analyses provided tentative support for an asthma/lung function susceptibility locus (48.9-49.1Mbps), and fine mapping localized modest association to the PLAUR gene. PLAUR SNPs in the 5' region, intron 3, and 3' region are associated with asthma and BHR susceptibility and predict FEV1 and plasma PLAUR levels. SNPs in the 5' region showed association for asthma (2 populations), FEV1 (2 populations), and BHR (2 populations) phenotypes. SNPs in intron 3 showed association with asthma (2 populations) and BHR (3 populations). Importantly, the same 5' region and intron 3 SNPs were associated with plasma PLAUR levels. The same 5' region and 3' region SNPs were found to be determinants of FEV1 decline in subjects with asthma. CONCLUSION:This study represents the first report to identify PLAUR as a potential asthma susceptibility gene and determine PLAUR regions underlying this association, including a role in influencing plasma PLAUR levels. Finally, the association of PLAUR with lung function decline supports a role for PLAUR in airway remodeling in asthma.

Airway hyper-responsiveness (AHR) is a key feature of asthma and a causal relationship between airway inflammation and AHR has been identified. The aim of the current study was to clarify the effect of proinflammatory cytokines and asthma medication on primary human airway smooth muscle (ASM) inositol phosphate (IPx) signalling and define the regulatory loci involved.

The Large(myd) mouse has a loss-of-function mutation in the putative glycosyltransferase gene Large. Mutations in the human homolog (LARGE) have been described in a form of congenital muscular dystrophy (MDC1D). Other genes (POMT1, POMGnT1, fukutin, and FKRP) that encode known or putative glycosylation enzymes are also causally associated with human congenital muscular dystrophies. All these diseases are associated with hypoglycosylation of the membrane protein alpha-dystroglycan (alpha-DG) and consequent loss of extracellular ligand binding. Hence, they are termed dystroglycanopathies. A paralogous gene for LARGE (LARGE2 or GYLTL1B) may also have a role in DG glycosylation. Using database interrogation and reverse-transcriptase polymerase chain reaction (RT-PCR), we identified vertebrate orthologs of each of these LARGE genes in many vertebrates, including human, mouse, dog, chicken, zebrafish, and pufferfish. However, within invertebrate genomes, we were able to identify only single homologs. We suggest that vertebrate LARGE orthologs be referred to as LARGE1. RT-PCR, dot-blot, and northern analysis indicated that LARGE2 has a more restricted tissue-expression profile than LARGE1. Using epitope-tagged proteins, we show that both LARGE1 and LARGE2 localize to the Golgi apparatus. The high similarity between the LARGE paralogs suggests that LARGE2 may also act on DG. Overexpression of LARGE2 in mouse C2C12 myoblasts results in increased glycosylation of alpha-DG accompanied by an increase in laminin binding. Thus, there may be functional redundancy between LARGE1 and LARGE2. Consistent with this idea, we show that alpha-DG is still fully glycosylated in kidney (a tissue that expresses a high level of LARGE2 mRNA) of Large(myd) mutant mice.

The myodystrophy (Large(myd)) mouse has a spontaneous loss of function mutation in a putative glycosyltransferase gene (Large). Mutations in the human gene (LARGE) have been described in congenital muscular dystrophy type 1D (MDC1D). Mutations in four other genes that encode known or putative glycosylation enzymes (POMT1, POMGnT1, fukutin and FKRP) are also associated with muscular dystrophy. In all these diseases hypoglycosylation of alpha-dystroglycan, and consequent loss of ligand binding, is a common pathomechanism. Currently, the Large(myd) mouse is the principal animal model for studying the underlying molecular mechanisms of this group of disorders. Over-expression of LARGE in cells from patients with mutations in POMT1 or POMGnT1 results in hyperglycosylation of alpha-dystroglycan and restoration of laminin binding. Thus, LARGE is a potential therapeutic target. Here, we define the intronic deletion breakpoints of the Large(myd) mutation and describe a simple, PCR-based diagnostic assay, facilitating the study of this important animal model.