Two new polymorphic markers in the human proα2(1) collagen gene

Summary Structural defects in the human type 1 collagen genes are known to be the cause of several inherited disorders of connective tissue, such as osteogenesis imperfecta. The analysis and prenatal diagnosis of these disorders would be facilitated by establishing a set of polymorphic markers at these gene loci. We have previously reported the presence of an Msp 1 restriction fragment length polymorphism in the pro2(1) collagen genes of several Southern African populations (Grobler-Rabie et al., in press). This report describes the detection of a Bgl II and an EcoRI polymorphism in the pro2 gene of South African Blacks.     

Partial structure of the human α2(IV) collagen chain and chromosomal localization of the gene (COL4A2)

Summary We have isolated a 2.1-kb cDNA clone from a human placental library encoding part of the 2 chain of collagen IV, a major structural protein of basement membranes. The DNA sequence encodes 446 amino acids in the triplehelical domain plus the 227 amino acids of the carboxy-terminal globular domain. The latter structure is composed of two homologous subdomains and is highly conserved between the 1 and 2 chains. The triple-helical domain contained seven interruptions of the Gly-X-Y repeat and these interruptions were in general larger than their counterparts in the 1 chain. DNA from human rodent hybrid cell lines was analyzed under conditions in which there was no cross-hybridization of the 2(IV) cDNA probe with the gene for the 1(IV) collagen chain. An Eco RI fragment characteristic of the 2 chain had a concordance of 0.97 with chromosome 13. This result was confirmed and extended with in situ localization of the gene at 13q34. Since the 1(IV) gene has previously been localized to 13q34, the two type IV collagen genes reside in the same chromosome region (13q34), possibly in a gene cluster. The presence of the genes for type IV collagen chains on chromosome 13 excludes a primary role for these genes in adult polycystic kidney disease and X-linked forms of hereditary nephritis.     

Generation of pigs with humanized type Ⅱ collagen by precise human COL2A1 gene knock-in

<正>Osteoarthritis (OA) is the most common chronic disease, characterized by progressive cartilage breakdown, subchondral bone sclerosis, and aberrant bone outgrowth (Yucesoy et al., 2015; Hussain et al., 2016). OA is one of the leading causes of cartilage damage. Patients with severe cartilage damage require transplantation of articular cartilage to improve their quality of life. Type Ⅱ collagen is a major component of articular cartilage and intervertebral discs and plays an important rol...     

Deletion 14q(q24.3 to q32.1) syndrome: significance of peculiar facial appearance in its diagnosis,and deletion mapping of (α1-antitrypsin)

Summary A 10-month-old Japanese boy who had interstitial deletion of the long arm of chromosome No. 14; 46,XY, del(14)(pter»q24.3::q32.1»qter) is reported. A peculiar facial appearance, including round face, frontal hypertrichosis with thick eyebrows, horizontal narrow palpebral fissures, a short bulbous nose with a flat nasal root, and mild micrognathia, appeared to be common with the two previously reported cases. We stress the significance of this peculiar facial appearance in the diagnosis of 14q-(q24.3 to q32.1) syndrome. The level of ₁-antitrypsin in the patient was only about half of that of his parents and controls, and the Pi locus was tentatively assigned to band 14q32.1.     

Cysteine in the triple helical domain of the proα2(I) chain of type-I collagen in nonlethal forms of osteogenesis imperfecta

Summary To determine if some individuals with deforming varieties of osteogenesis imperfecta (OI) carry point mutations in the COL1A2 gene of type-I collagen, we examined collagens synthesized by cell strains from affected individuals for the presence of cysteine in the triple helical domain of the 2(I) chain, a domain from which it is normally excluded. We identified 4 individuals out of 60 whose cells synthesized a population of 2(I) chains with a cysteine residue in the triple helix. The clinical differences among the affected individuals and the heterogeneity in the locations of the cysteine residues suggest that the position of the substitution within the chain is important in determining the clinical phenotype. These data confirm that individuals with nonlethal OI may commonly harbor defects in the COL1A2 gene, and suggest that many of the defects are substitutions for glycine residues in the 2(I) triple helical domain.     

A base substitution at IVS-19 3′-end splice junction causes exon 20 skipping in proα2(I) collagen mRNA and produces mild osteogenesis imperfecta

Molecular investigations on a young patient and her family were undertaken to identify the molecular defect responsible for a mild form of osteogenesis imperfecta (OI) with blue sclerae, dentinogenesis imperfecta and joint laxity. Analysis of collagenous proteins from the proband's fibroblasts showed the presence of two populations of 2(I) chains, one normal and one migrating faster on SDS gels, thereby suggesting deletion of amino acid sequences. The faster migrating chains were retained mainly in the cell layer and not found in the extracellular matrix deposited by cultured fibroblasts. Chemical cleavage of mismatch (CCM) analysis on the patient's pro2(I) mRNA:normal cDNA heteroduplexes localized the molecular defect. cDNA sequencing revealed a deletion of exon 20 (54 bp) in about half of the molecules. Genomic DNA sequencing revealed heterozygosity for a G-to-C transversion of the last nucleotide of intron 19, which changed the 3 consensus splicing site. As a consequence pro2(I)mRNA was abnormally spliced from the last codon of exon 19 to the first codon of exon 21. To our knowledge, this is the first acceptor site mutation so far described in an OI patient. Restriction analysis indicated that the mutation was present also in three other affected family members. The full sequence of COL1A2 introns 19 and 20 are reported.     

Regional chromosomal localisation of APOA2 to 1q21–1q23

Summary Using in situ hybridisation, we have mapped APOA2 to the 1q21–1q23 region of chromosome 1. DNA hybridisation to somatic cell hybrids made from cells carrying a balanced translocation between X and 1 confirms the localisation as proximal to 1q23. This was further confirmed by the presence of two polymorphic alleles in a cell line carrying a deletion of 1q25–1q32.     

Recurrence of osteogenesis imperfecta because of paternal mosaicism: Gly862→Ser substitution in a type I collagen gene (COL1A1)

We determined that two siblings with type III osteogenesis imperfecta (OI) had the same single base substitution that converted the codon for glycine (Gly) 862 to a codon for serine (Ser) in exon 44 of the 1 chain of the type I ( 1(I)) collagen gene (COL1A1). The mutation was also detected in various paternal tissues; the mutant allele accounted for approximately 11% of the COL1A1 alleles in blood, 24% of those in fibroblasts, and 43% of those in sperm determined by allele-specific colony hybridization using amplified genomic sequences. These findings demonstrate that germ-line mosaicism in the phenotypically normal father is responsible for the recurrence. There is a cluster of serine substitutions for Gly (Gly⁸³², Gly⁸⁴⁴ and Gly⁹⁰¹) which is associated with nonlethal phenotypes and which is located between two lethal clusters. In the cases studied here, a Gly⁸⁶²Ser mutation was identified that is located inside the nonlethal cluster.     

A locus for juvenile myoclonic epilepsy maps to 2q33–q36

We performed a whole genome linkage analysis in a three-generation south Indian family with multiple members affected with juvenile myoclonic epilepsy (JME). The maximum two-point LOD score obtained was 3.32 at recombination fraction (θ) = 0 for D2S2248. The highest multipoint score of 3.59 was observed for the genomic interval between D2S2322 and D2S2228 at the chromosomal region 2q33–q36. Proximal and distal boundaries of the critical genetic interval were defined by D2S116 and D2S2390, respectively. A 24-Mb haplotype was found to co-segregate with JME in the family. While any potentially causative variant in the functional candidate genes, SLC4A3, SLC23A3, SLC11A1 and KCNE4, was not detected, we propose to examine brain-expressed NRP2, MAP2, PAX3, GPR1, TNS1 and DNPEP, and other such positional candidate genes to identify the disease-causing gene for the disorder.     

SSCP detection of a Gly565Val substitution in the proα(I) collagen chain resulting in osteogenesis imperfecta type II

A patient with perinatal lethal osteogenesis imperfecta (OI) type II has been studied in order to identify the causative mutation. By analysis of the type I collagen produced by cultured fibroblasts from the patient, the defect was mapped to 1 cyanogen bromide peptide 7, a region corresponding to 271 amino acid residues of either the 1(I) or 2(I) collagen chains. Polymerase chain reaction (PCR) amplification of the corresponding region of the 1(I) mRNA followed by single-strand conformation polymorphism analysis of restriction enzyme digestions of the PCR products allowed further mapping of the mutation to a small region of COL1A1. A heterozygous transversion of G to T within the last glycine codon of exon 32 was identified by DNA sequence analysis. This resulted in the substitution of glycine-565 by a valine residue, disrupting the repeating Gly-Xaa-Yaa sequence that is obligatory for correct formation of the collagen molecule. The mutation was shown to have occurred de novo and is thought to result in the OI phenotype.     

De novo and inherited mutations in COL4A2, encoding the type IV collagen α2 chain cause porencephaly

Porencephaly is a neurological disorder characterized by fluid-filled cysts or cavities in the brain that often cause hemiplegia. It has been suggested that porencephalic cavities result from focal cerebral degeneration involving hemorrhages. De novo or inherited heterozygous mutations in COL4A1, which encodes the type IV α1 collagen chain that is essential for structural integrity for vascular basement membranes, have been reported in individuals with porencephaly. Most mutations occurred at conserved Gly residues in the Gly-Xaa-Yaa repeats of the triple-helical domain, leading to alterations of the α1α1α2 heterotrimers. Here we report on two individuals with porencephaly caused by a heterozygous missense mutation in COL4A2, which encodes the type IV α2 collagen chain. Mutations c.3455G>A and c.3110G>A, one in each of the individuals, cause Gly residues in the Gly-Xaa-Yaa repeat to be substituted as p.Gly1152Asp and p.Gly1037Glu, respectively, probably resulting in alterations of the α1α1α2 heterotrimers. The c.3455G>A mutation was found in the proband's mother, who showed very mild monoparesis of the left upper extremity, and the maternal elder uncle, who had congenital hemiplegia. The maternal grandfather harboring the mutation is asymptomatic. The c.3110G>A mutation occurred de novo. Our study confirmed that abnormalities of the α1α1α2 heterotrimers of type IV collagen cause porencephaly and stresses the importance of screening for COL4A2 as well as for COL4A1.     

α_(1A)-adrenergic receptor mediated pressor response to phenylephrine in anesthetized rat

To determine which subtype of α1-adrenergic receptors plays a role in the regulation of blood pressure, with α1A-adrenergic receptor-mediated vasoconstriction in perfused hindlimb as a control, we compared the inhibitory effects of various ai-adrenergic receptor selective antagonists on the vasopressure responses to phenylephrine between the mean arterial pressure and hindlimb perfusion pressure in anesthetized rats. In Normotensive Wistar rats, the results showed that the inhibitory effects (dose ratios of ED50, Dr) of α1-adrenoceptor selective antagonist (prazosin, Dr 13.5±3.6 vs.15.1±4.3, n = 11), α1A-adrenoceptor selective antagonist (5-methyl-urapidil, Dr 2.4±0.9 vs. 3.7±2.3, n = 12; RS-17053, Dr 3.2±1.6 vs. 4.4±3.3, n =12) and α1D-adrenoceptor selective antagonist (BMY7378, Dr 1.9±0.9 vs. 2.2±0.8, n = 8) on phenylephrine- induced increases of perfusion pressure in the autoperfused femoral beds were the same as that in the mean arterial blood pressure in normotensive Wistar rats. The i     

Human interferon gamma receptor 1 (IFNGR1) gene maps to chromosome region 6q23–6q24

Summary The human interferon receptor (IFNGR1) gene has been localized by in situ hybridization to chromosome 6 at q23–q24. This chromosomal region is often deleted in lymphoid cell malignancies.     

Pure monosomy and trisomy 2q24.2→q3105 due to an inv ins(7;2)(q21.2;q3105q24.2) segregating in four generations

Summary An inv ins(7;2)(q21.2;q3105q24.2) was found to segregate through four generations of a family. Adjacent-1 segregation aneusomies were ascertained in five patients: three monosomics and two trisomics; and the corresponding syndromes were delineated. The comparative analysis between these and other previously described 2q aneusomic individuals led to the conclusion that a large cleft between first and second toes is a constant feature in monosomy 2q24q31. No other trait could plausible be mapped. Risks of 7.9 to 31.9% for aneusomic children and of 26.3% for abortion were estimated in the present family.     

A new locus for autosomal dominant Charcot-Marie-Tooth disease type 2 (CMT2L) maps to chromosome 12q24

Charcot-Marie-Tooth disease (CMT) is one of the most common inherited neurological disorders with a prevalence estimated at 1/2500. The axonal form of this disorder is referred to as Charcot-Marie-Tooth type 2 disease (CMT2). Recently, a large Chinese family with CMT2 was found in the Hunan and Hubei provinces of China. The known loci for CMT1A, CMT2D, CMT1B (the same locus is also responsible for CMT2I and CMT2J), CMT2A, CMT2E, and CMT2F were excluded in this family by linkage analysis. A genome-wide screening was then carried out, and the results revealed linkage of CMT2 to a locus at chromosome 12q24. Haplotype construction and analyses localized this novel locus to a 6.8-cM interval between microsatellite markers D12S366 and D12S1611. The maximal two-point LOD score of 6.35 and multipoint LOD score of 8.08 for marker D12S76 at a recombination fraction () of 0 strongly supported linkage to this locus. Thus, CMT2 neuropathy in this family represents a novel genetic entity that we have designated as CMT2L.     

Length polymorphism in the pro α2(I) collagen gene: an alternative explanation in a case of Marfan syndrome

Summary A 38 base pair (bp) insertion in the pro 2(I) collagen gene (COL1A2) of a patient with Marfan syndrome has been proposed to be the possible cause of the disease (Henke et al. 1985). However, analysis of this insertion in DNA from the patient in question and from random normal individuals reveals it to be a common polymorphism. We suggest that the 38 bp insertion is not related to the primary defect in this case of Marfan syndrome.