PCR detection of five restriction site dimorphisms at the type I collagen loci COL1A1 and COL1A2.
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Biomedical subjects
Publications and source records attributed to L Priestley.
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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.
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.
Amplification of a variable region 3' to the human type II collagen gene (COL2A1) has permitted segregation analysis in a three generation Stickler syndrome pedigree. This family had previously proved uninformative for the known restriction fragment length dimorphisms. Amplification of the variable region revealed five distinguishable alleles, of which three were segregating in this family. The lod score in favour of linkage was 2.86 at zero recombination.
The basal metabolic rate (BMR) was determined in 14 pairs of monozygotic (MZ; 11 females, 3 males) and 12 pairs of dizygotic (DZ; 10 females, 2 males) twins, with mean ages of 22.7 and 26 years. Zygosity was confirmed using DNA fingerprinting. When BMR was expressed as kJ/d, kJ/kg/d and kJ/kg FFM/d significant intra-class correlation coefficients were observed in the MZ twins of 0.82, 0.79 and 0.85, respectively. The DZ twins showed much lower intra-class correlations coefficients of 0.1, 0.07 and -0.04. Although the results of the study suggest a likely genetic component to the variation in BMR, they should be interpreted with caution as heritability estimates vary with the method of calculation. These will be critically discussed in the paper.
Seventy-seven persons with a variety of heritable chondrodysplasias were screened for gross rearrangements of the structural gene encoding the major cartilage collagen, collagen II. None was found. Segregation of the locus (COL2A1) was studied in 19 pedigrees using three restriction site dimorphisms (shown by PvuII, HindIII, and BamHI) and a length polymorphism as linkage markers. Discordant segregation between COL2A1 and the mutant locus was seen in pedigrees with multiple epiphyseal dysplasia, autosomal recessive spondyloepiphyseal dysplasia tarda, hypochondroplasia, pseudoachondroplasia, diaphyseal aclasis, and trichorhinophalangeal syndrome. One pedigree with diastrophic dysplasia was weakly concordant. Autosomal dominant spondyloepiphyseal dysplasia tarda and metaphyseal chondrodysplasia (type Schmid) were not informative. We conclude that mutations of the collagen II gene are not a common feature of the heritable chondrodysplasias. Since the chondrocyte binding protein, chondrocalcin, is also encoded at COL2A1 our conclusions apply equally to this gene.
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The insulin-like growth factors (IGF) I and II are single-chain serum proteins of 70 and 67 amino acids, respectively, which are synthesized by the liver and possibly other tissues. They are probably required for normal fetal and postnatal growth and development. They also stimulate the growth of cultured cells, possibly by controlling the progression through the G1 phase of the cell cycle. In contrast to IGF-II whose concentration does not vary during postnatal development, the serum levels of IGF-I increase several-fold to adult levels during puberty. The serum concentration of IGF-I is a sensitive monitor of growth hormone levels and is decreased in individuals with growth hormone deficiency and elevated in those with growth hormone-secreting tumours. As a first step in studying the biosynthesis of these proteins and elucidating their role(s) in normal development and in tumorigenesis, we have isolated and sequenced cDNAs prepared from adult human liver mRNA which encode the precursors to IGF-I and -II. We report here the sequence of a cDNA encoding a 180-amino acid protein which is the precursor to IGF-II.