Lynne E. Vinall

Variable number tandem repeat polymorphism of the mucin genes located in the complex on 11p15.5

Abstract A family of four genes that encode major secreted mucins (MUC6, MUC2, MUC5AC and MUC5B) map to within 400kb on chromosome 11p15.5. These genes contain long stretches of tandem repeats of sequence that encode serine- and threonine-rich domains but that otherwise show no similarity from gene to gene, and regions of unique sequence domains that do show evidence of sequence homology. We have previously reported the existence of polymorphism in three of these genes but the extent and nature of this allelic variation is now described here in detail. Variable number tandem repeat polymorphisms of MUC6, MUC2 and MUC5AC are predicted to encode mucin polypeptides that differ in length. In the case of MUC2 and MUC6 these length differences are substantial (up to twofold). MUC5B in contrast does not show common allele length variation. Three MUC2 mutations are reported, none of which are associated with the meiotic recombinations previously observed in this region of chromosome 11.

Contribution of functional variation in the IL13 gene to allergy, hay fever and asthma in the NSHD longitudinal 1946 birth cohort

Background:  Genetic variants of the two adjacent genes, IL13 and IL4 have frequently been reported as being associated with susceptibility to atopy and asthma, both in adults and children, and some studies also suggest association with lung function and chronic obstructive pulmonary disease.

Genetic polymorphism of MUC7: Allele frequencies and association with asthma

MUC7 encodes a small salivary mucin, previously called MG2, a glycoprotein with a putative role in facilitating the clearance of oral bacteria. The central domain of this glycoprotein was previously shown to comprise five or six tandemly repeated units of 23 amino-acids which carry most of the O-linked glycans. The polymorphism of these two allelic forms (MUC7*5 or MUC7*6) has been confirmed in this study in which we have analysed a large cohort of subjects (n = 375) of various ethnic origins. We have also identified a novel rare allele with eight tandem repeats (MUC7*8). MUC7*6 was the most common allele (0.78–0.95) in all the populations tested. The tandem repeat arrays of 22 MUC7*5 alleles and 34 MUC7*6 alleles were sequenced. No sequence differences were detected in any of the MUC7*6 alleles. Twenty-one MUC7*5 alleles sequenced lacked the 4th tandem repeat (structure TR12356), while one showed the structure TR12127. The structure of the MUC7*8 allele was TR12343456. Because of the known role of MUC7 in bacterial binding, and thus its potential involvement in susceptibility to chest disease we also tested MUC7 in our previously described series of Northern European atopic individuals with and without associated asthma. The MUC7*5 allele was rarer in the atopic asthmatics than in the atopic non-asthmatics (P = 0.014, OR for no asthma in atopic individuals 3.13, CI 1.01–6.10), and the difference in frequency between all asthmatics and all non-asthmatics was statistically significant (P = 0.009) while there was no difference between atopy and non-atopy (P = 0.199). In this study we also report the electrophoretic analysis of the MUC7 glycoprotein in saliva from individuals of different MUC7 genotype.

MUC7 haplotype analysis: results from a longitudinal birth cohort support protective effect of the MUC7*5 allele on respiratory function

The mucin MUC7 is a glycoprotein that plays a role in bacterial clearance and has candidacidal activity. There are two common allelic forms with 5 or 6 tandem repeats (TR) of a 23 amino acid motif within the highly glycosylated (mucin) domain. The MUC7*5 allele has previously been shown to be less prevalent in patients with asthma, suggesting a protective role in respiratory function. Here we report the characterisation of other frequent genetic variation within and in the vicinity of the gene MUC7. A total of 26 polymorphisms were identified of which 5 are located in transcribed regions. A subset of 8 polymorphisms was selected to represent the major haplotypes, and allelic association was studied in individuals of Northern European ancestry, including known asthmatics. There was low haplotype diversity and strong association between each of the loci, and the MUC7*5 allele‐carrying haplotype remained the one most strongly associated with asthma. Five of these polymorphisms have also been tested in the 1946 longitudinal birth cohort, for whom developmental, environmental and respiratory health data are available. We show that the haplotype carrying MUC7*5 is associated with higher FEV1 at 53 years, reduced age‐related decline of FEV1, and also reduced incidence of wheeze.

Ulcerative colitis is not associated with differences in MUC2 mucin allele length

Editor—The aetiology of inflammatory bowel disease (IBD) is complex and shows clear evidence of familial clustering,1-3 and genetic linkage studies suggest a number of susceptibility genes.4-12 Changes in mucin expression are a feature of IBD.13-17 In ulcerative colitis there is a depletion of mucus, while the reverse is true for Crohn’s disease.18 Since the gene that encodes a major component of gel forming mucin of the large intestine, MUC2, located on 11p15.5, shows a high level of genetically determined polymorphism in length,19-21 it has been considered as a potential risk factor in IBD.22We have previously shown that the allele lengths range in size between approximately 45 and 200 repeats as judged by cutting genomic DNA samples with the restriction enzyme Hin fI.19 This corresponds to apomucin sizes ranging from Mr 400-760 000. It is our hypothesis that these differences have a functional significance by changing the properties of the mucins in terms of the amount of apomucin backbone available for glycosylation or altering the spacing between the cysteine rich domains which are involved in cross linking or both. Here we report the work of …

MUC5AC and inflammatory mediators associated with respiratory outcomes in the British 1946 birth cohort.

Dysregulation of respiratory mucins, MUC5AC in particular, has been implicated in respiratory disease and MUC5AC expression is up‐regulated in response to environmental challenges and inflammatory mediators. The aim of this study was to examine the effect of genetic variation on susceptibility to common respiratory conditions.