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B Sykes

Publications and source records attributed to B Sykes.

At least 55 records · Page 3Linked to original sources
PubMed1994

Sibling pair analysis shows no linkage of generalized osteoarthritis to the loci encoding type II collagen, cartilage link protein or cartilage matrix protein.

Generalized OA (GOA) is a well-characterized subset of primary OA which is strongly associated with the occurrence of Heberden's nodes. Using gene-specific highly polymorphic markers and affected sib pair (ASP) analyses, we have investigated genetic linkage between GOA and three cartilage matrix genes: COL2A1 which encodes type II collagen; CRTL1 which encodes the cartilage link protein and CRTM which encodes the cartilage matrix protein. The analyses showed no linkage between GOA and the three genes in the 38 sib pairs examined. Since we examined a relatively modest number of sib pairs, our results can only exclude COL2A1, CRTL1 and CRTM as major susceptibility loci for GOA.

Alleles↗
PubMed1994

Differential allelic expression of a fibrillin gene (FBN1) in patients with Marfan syndrome.

Marfan syndrome is a connective-tissue disorder affecting cardiovascular, skeletal, and ocular systems. The major Marfan locus has been identified as the FBN1 gene on chromosome 15; this codes for the extracellular-matrix protein fibrillin, a 350-kD constituent of the 8-10-nm elastin-associated microfibrils. We identified five MFS patients who were heterozygous for an RsaI restriction-site dimorphism in the 3' UTR of the FBN1 gene. This expressed variation was used to distinguish the mRNA output from each of the two FBN1 alleles in fibroblast cultures from these five patients. Three of the patients were shown to produce < 5% of the normal level of FBN1 transcripts from one of their alleles. This null-allele phenotype was not observed in 10 nonmarfanoid fibroblast cell lines.

Adult↗
PubMed1993

Linkage analysis in dominantly inherited osteogenesis imperfecta.

The only serious attempts at linkage in osteogenesis imperfecta (OI) have shown that the disease is linked to type 1 collagen genes in all families studied in which it segregrates as a clear mendelian dominant trait. For prenatal diagnosis the probability that a new family is linked can be taken as greater than 0.95 and this figure is augmented as more meioses are studied. Some phenotype correlations, notably between the OI type IV phenotype and linkage to COL1A2 and between presenile hearing loss in OI type I and linkage to COL1A1, can be used to improve risk estimates substantially in families where there are no segregation data to distinguish whether COL1A1 or COL1A2 is the mutant locus.

Alleles↗
PubMed1993

Genomic organization of the sequence coding for fibrillin, the defective gene product in Marfan syndrome.

Marfan syndrome results from mutations in an extracellular matrix glycoprotein, fibrillin. Previous studies have characterized approximately 6.9-kb of the estimated 10-kb fibrillin transcript. We have now completed the primary structure of fibrillin, elucidated the exon/intron organization of the gene and derived a physical map of the genetic locus. Pre-fibrillin consists of 2,871 amino acids which, excluding the signal peptide, are arranged into five structurally distinct regions. The largest of these regions comprises about 75% of the entire protein and consists of numerous repeated cysteine-rich sequences homologous to the peptide motifs of the epidermal growth factor (EGF) and transforming growth factor-beta binding protein (TGF-bp). Forty-three of the forty-six EGF-like repeats contain a calcium binding consensus sequence (EGF-CB) conceivably mediating protein-protein interactions. Fibrillin exhibits a few additional cysteine-rich modules that are apparently unique to this macromolecule and may represent evolutionary variants of the EGF-CB and TGF-bp motifs. Almost all of the cysteine-rich repeats are encoded by single exons; consequently, the fibrillin gene is relatively large (approximately 110-kb) and highly fragmented (65 exons). This study provides the first comprehensive analysis of the fibrillin gene and relevant information for the full characterization of Marfan syndrome mutations.

Amino Acid Sequence↗
PubMed1993

Osteogenesis imperfecta type III: mutations in the type I collagen structural genes, COL1A1 and COL1A2, are not necessarily responsible.

Most forms of osteogenesis imperfecta are caused by dominant mutations in either of the two genes, COL1A1 and COL1A2, that encode the pro alpha 1(I) and pro alpha 2(I) chains of type I collagen, respectively. However, a severe, autosomal recessive form of OI type III with a comparatively high frequency has been recognised in the black populations of southern Africa. We preformed linkage analyses in eight OI type III families using RFLPs associated with the COL1A1 and COL1A2 loci to determine whether mutations in the genes for type I collagen were responsible for this form of OI. Recombination between the OI phenotype and polymorphic markers at both loci was shown in three of the eight families investigated. The combined lod scores for the eight families were -10.6 for COL1A1 and -11.2 for COL1A2. Further, we examined the type I procollagen produced by skin fibroblast cultures derived from 15 affected and 12 unaffected subjects from the above eight families plus one further family. We found no evidence for defects in the synthesis, structure, secretion, or post-translational modification of the chains of type I procollagen produced by any of the family members. These results suggest that mutations within or near the type I collagen structural genes are not responsible for this form of OI.

Africa, Southern↗
PubMed1992

No evidence for involvement of type 1 collagen structural genes in 'genetic predisposition' to alcoholic cirrhosis.

Type 1 collagen is the predominant collagen in cirrhotic livers. Each type 1 collagen molecule contains three subunits, two are identical (the alpha 1 chains) and the sequence of the third (alpha 2) is very similar. They are encoded at the non-synthenic loci, COL1A1 and COL1A2 and restriction site dimorphisms have been described at each locus. Genetic factors have been invoked as a basis for increased susceptibility to alcoholic cirrhosis. One hypothesis is that genetically determined differences in type 1 collagen may be involved in this predisposition. We have examined this by analysing restriction fragment length polymorphisms at each type 1 collagen locus in leucocyte DNA from 56 unrelated patients with alcoholic cirrhosis and 74 local unrelated healthy controls. Based on the presence or absence of these restriction site dimorphisms four possible haplotypes were generated at COL1A1 and COL1A2. We found no significant difference in allele frequencies between alcoholic cirrhotics and controls and, unlike a previous small study, we found no particular haplotype of either gene was associated with alcoholic cirrhosis. Our study provides no evidence for involvement of type 1 collagen structural genes in a genetic predisposition to cirrhosis in alcoholics.

Collagen↗
PubMed1992

SSCP and segregation analysis of the human type X collagen gene (COL10A1) in heritable forms of chondrodysplasia.

Type X collagen is a homotrimeric, short chain, nonfibrillar collagen that is expressed exclusively by hypertrophic chondrocytes at the sites of endochondral ossification. The distribution and pattern of expression of the type X collagen gene (COL10A1) suggests that mutations altering the structure and synthesis of the protein may be responsible for causing heritable forms of chondrodysplasia. We investigated whether mutations within the human COL10A1 gene were responsible for causing the disorders achondroplasia, hypochondroplasia, pseudoachondroplasia, and thanatophoric dysplasia, by analyzing the coding regions of the gene by using PCR and the single-stranded conformational polymorphism technique. By this approach, seven sequence changes were identified within and flanking the coding regions of the gene of the affected persons. We demonstrated that six of these sequence changes were not responsible for causing these forms of chondrodysplasia but were polymorphic in nature. The sequence changes were used to demonstrate discordant segregation between the COL10A1 locus and achondroplasia and pseudoachondroplasia, in nuclear families. This lack of segregation suggests that mutations within or near the COL10A1 locus are not responsible for these disorders. The seventh sequence change resulted in a valine-to-methionine substitution in the carboxyl-terminal domain of the molecule and was identified in only two hypochondroplasic individuals from a single family. Segregation analysis in this family was inconclusive, and the significance of this substitution remains uncertain.

Base Sequence↗
PubMed1992

Segregation of structural collagen genes in adolescent idiopathic scoliosis.

The etiology of idiopathic scoliosis remains unknown. The condition results in a characteristic deformity of the spine and surrounding tissues. Both Types I and II collagen are important constituents of the affected tissues, and thus defective collagens are reasonable candidates for the primary abnormality in adolescent idiopathic scoliosis (AIS). Direct analyses of the amount and solubility of collagen have revealed differences between normal individuals and those with AIS. However, these changes may be secondary to the mechanical effects of the spinal deformity. Segregation analysis was done of genetic markers linked to the structural genes encoding Types I and II collagen to test these candidate loci in four pedigrees with dominantly inherited AIS. In one pedigree, markers linked to both of the Type I collagen loci (COL1A1 and COL1A2) were found to be inherited independently of the abnormal phenotype. Two pedigrees were discordant at one of the Type I loci. The condition also segregated independently of the locus for Type II collagen (COL2A1) in three pedigrees. This is evidence against idiopathic scoliosis generally being caused by mutations in the Types I and II collagen genes.

Adolescent↗
PubMed1991

A limited association of generalized osteoarthritis with alleles at the type II collagen locus: COL2A1.

A significant genetic influence in osteoarthritis has been observed in the combination of Heberden's nodes and generalized osteoarthritis. We examined whether mutation in the gene encoding the major cartilage matrix protein type II collagen was responsible by comparing allele frequencies at the locus (COL2A1) in a group of 61 patients with nodal GOA with a control population and by analysing the COL2A1 genotypes of 21 affected sibling pairs. There were no significant allele differences but a slightly increased tendency over chance alone for affected siblings to have inherited the same COL2A1 alleles from their parents.

Alleles↗
PubMed1991

Prenatal diagnosis of osteogenesis imperfecta by identification of the concordant collagen 1 allele.

Dominantly inherited osteogenesis imperfecta is consistently linked to the two loci encoding the alpha 1 and alpha 2 subunits of collagen 1, the predominant bone collagen. We have performed several prenatal diagnoses based on identification of the segregating allele at the concordant locus in chorionic villus samples both in families where the linkage can be independently shown and in those where it cannot. Especially in the latter category, calculation of the final risk must incorporate an estimate of genetic heterogeneity within the OI population to give a prior probability of linkage. This figure can then be modified for each family by additional information from concordant meioses.

Alleles↗