Major rearrangements in the alpha 5(IV) collagen gene in three patients with Alport syndrome.

The gene coding for the alpha 5 chian of type IV collagen (alpha 5(IV) collagen), which maps to Xq22, is a candidate gene for the X-linked dominant disease Alport syndrome (AS). Using three cDNA clones, covering the 3' end of the alpha 5(IV) collagen gene, 3 of 38 patients have been identified with mutations in this gene. Each of these patients shows a gross rearrangement of DNA: a deletion of at least 35 kb, an insertion/deletion event involving approximately 25 kb, and a duplication of at least 35 kb of DNA.     

Molecular cloning of the c-fms locus and its assignment to human chromosome 5

Molecular clones of the retroviral oncogene v-fms were used to isolate recombinant bacteriophages containing c-fms proto-oncogene sequences from a human placental DNA library. Viral and cellular fms sequences were used in Southern blotting experiments with a panel of 32 human X mouse somatic cell hybrids to assign the human c-fms proto-oncogene to human chromosome 5.     

Single base mutation in alpha 5(IV) collagen chain gene converting a conserved cysteine to serine in Alport syndrome.

We have identified a point mutation in the type IV collagen alpha 5 chain gene (COL4A5) in Alport syndrome. Variant PstI (Barker et al., 1990, Science 248, 1224-1227), and BglII restriction sites with complete linkage with the Alport phenotype have been found in the 3' end of the COL4A5 gene in the large Utah Kindred P. The approximate location of the variant sites was determined by restriction enzyme mapping, after which this region of the gene (1028 bp) was amplified with the polymerase chain reaction (PCR) from DNA of normal and affected individuals for sequencing analysis. The PCR products showed the absence or presence of the variant PstI and BglII sites in DNA from normal and affected individuals, respectively. DNA sequencing revealed a single base change in exon 3 (from the 3' end) in DNA from affected individuals, changing the TGT codon of cysteine to the TCT codon for serine. This single base mutation also generated new restriction sites for PstI and BglII. The mutation involves a cysteine residue that has remained conserved in the carboxyl-end noncollagenous domain (NC domain) of all known type IV collagen alpha chains from Drosophila to man. It is presumably crucial for maintaining the right conformation of the NC domain, which is important for both triple-helix formation and the formation of intermolecular cross-links of type IV collagen molecules.     

Molecular and functional defects in kidneys of mice lacking collagen alpha 3(IV): implications for Alport syndrome

Collagen IV is a major structural component of all basal laminae (BLs). Six collagen IV alpha chains are present in mammals; alpha 1 and alpha 2(IV) are broadly expressed in embryos and adults, whereas alpha 3- 6(IV) are restricted to a defined subset of BLs. In the glomerular BL of the kidney, the alpha 1 and alpha 2(IV) chains are replaced by the alpha 3-5(IV) chains as development proceeds. In humans, mutation of the collagen alpha 3, alpha 4, or alpha 5(IV) chain genes results in a delayed onset renal disease called Alport syndrome. We show here that mice lacking collagen alpha 3(IV) display a renal phenotype strikingly similar to Alport syndrome: decreased glomerular filtration (leading to uremia), compromised glomerular integrity (leading to proteinuria), structural changes in glomerular BL, and glomerulonephritis. Interestingly, numerous changes in the molecular composition of glomerular BL precede the onset of renal dysfunction; these include loss of collagens alpha 4 and alpha 5(IV), retention of collagen alpha 1/2(IV), appearance of fibronectin and collagen VI, and increased levels of perlecan. We suggest that these alterations contribute, along with loss of collagen IV isoforms per se, to renal pathology.     

DNA rearrangements in the alpha 5(IV) collagen gene (COL4A5) of individuals with Alport syndrome: further refinement using pulsed-field gel electrophoresis.

Alport syndrome (AS), an X-linked kidney disorder, has been shown to be caused by mutations in the gene for the alpha 5-chain of type IV collagen (COL4A5), which maps to Xq22. On the basis of the results of conventional Southern blot analysis of AS patient DNAs, we employed pulsed-field gel electrophoresis to characterize further three gene rearrangements at the 3'-end of alpha 5(IV). We were able to construct long-range restriction maps for all three of these patients and deduce the extent and nature of each rearrangement. One of these mutations is a 450-kb simple deletion that includes 12 kb of the alpha 5(IV) gene. A second mutation has been shown to be a direct duplication of 35 kb of alpha 5(IV) genomic DNA, and a third mutation involves a complex insertion/deletion event resulting in an overall loss of 25 kb.     

Molecular cloning of human lysyl oxidase and assignment of the gene to chromosome 5q23.3-31.2.

Lysyl oxidase (EC 1.4.3.13) initiates the crosslinking of collagens and elastin by catalyzing oxidative deamination of the epsilon-amino group in certain lysine and hydroxylysine residues. We report here on the isolation and characterization of cDNA clones for the enzyme from human placenta and rat aorta lambda gt11 cDNA libraries. A cDNA clone for human lysyl oxidase covers all the coding sequences, 230 nucleotides of the 5' and 299 nucleotides, of the 3' untranslated sequences, including a poly(A) tail of 23 nucleotides. This cDNA encodes a polypeptide of 417 amino acid residues, including a signal peptide of 21 amino acids. Sequencing of two rat lysyl oxidase cDNA clones indicated six differences between the present and the previously published sequence for the rat enzyme [Trackman et al. (1990) Biochemistry 29: 4863-4870], resulting in frameshifts in the translated sequence. The human lysyl oxidase sequence was found to be 78% identical to the revised rat sequence at the nucleotide level and 84% identical at the amino acid level, with the degree of identity unevenly distributed between various regions of the coded polypeptide. Northern blot analysis of human skin fibroblasts RNA indicated that the human lysyl oxidase cDNA hybridizes to at least four mRNA species; their sizes are about 5.5, 4.3, 2.4, and 2.0 kb. Analysis of a panel of 25 human x hamster cell hybrids by Southern blotting mapped the human lysyl oxidase gene to chromosome 5, and in situ hybridization mapped it to 5q23.3-31.2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mapping of Alport syndrome to the long arm of the X chromosome.

Five X-chromosome DNA markers were typed on 261 members of three large kindreds with Alport syndrome (hereditary glomerulonephritis). Lod scores greater than 3.0 for linkage between the disease locus and two of the markers confirmed X-linked inheritance of the disease. A decreasing gradient in the estimated recombination fractions observed when the markers were ordered on the basis of their map locations suggested that the disease locus is on the long arm distal to all the markers typed in this study. Using three-locus analysis we rejected all but three map orders for the six loci (the disease locus and five markers). In all three the Alport syndrome locus was on the long arm of the X chromosome distal to all the markers. Two types of Alport syndrome were represented in the three kindreds. Affected males in one kindred developed deafness in addition to nephritis; deafness did not occur in members of the other two kindreds. Although larger recombination-fraction estimates were obtained for all five markers in the kindreds without deafness, the difference was significant for only one marker. Evidence of heterogeneity was not found in tests using two markers. Markers distal to the disease locus are needed to determine whether two loci are responsible for the two types of Alport syndrome.     

Identification of noncollagenous sites encoding specific interactions and quaternary assembly of alpha 3 alpha 4 alpha 5(IV) collagen: implications for Alport gene therapy

Defective assembly of alpha 3 alpha 4 alpha 5(IV) collagen in the glomerular basement membrane causes Alport syndrome, a hereditary glomerulonephritis progressing to end-stage kidney failure. Assembly of collagen IV chains into heterotrimeric molecules and networks is driven by their noncollagenous (NC1) domains, but the sites encoding the specificity of these interactions are not known. To identify the sites directing quaternary assembly of alpha 3 alpha 4 alpha 5(IV) collagen, correctly folded NC1 chimeras were produced, and their interactions with other NC1 monomers were evaluated. All alpha1/alpha 5 chimeras containing alpha 5 NC1 residues 188-227 replicated the ability of alpha 5 NC1 to bind to alpha3NC1 and co-assemble into NC1 hexamers. Conversely, substitution of alpha 5 NC1 residues 188-227 by alpha1NC1 abolished these quaternary interactions. The amino-terminal 58 residues of alpha3NC1 encoded binding to alpha 5 NC1, but this interaction was not sufficient for hexamer co-assembly. Because alpha 5 NC1 residues 188-227 are necessary and sufficient for assembly into alpha 3 alpha 4 alpha 5 NC1 hexamers, whereas the immunodominant alloantigenic sites of alpha 5 NC1 do not encode specific quaternary interactions, the findings provide a basis for the rational design of less immunogenic alpha 5(IV) collagen constructs for the gene therapy of X-linked Alport patients.     

Construction of a yeast artificial chromosome contig encompassing the human alpha 5(IV) collagen gene (COL4A5).

A PCR-based screening approach was used to isolate six yeast artificial chromosome (YAC) clones containing segments of the human alpha 5(IV) collagen gene (COL4A5). This gene is located at Xq22 and is known to be involved in the kidney disorder known as Alport syndrome (AS). By analyzing sequence-tagged sites, cDNA content, and rare-cutting restriction site patterns in these YAC clones, a contig that spans the entirety of the alpha 5(IV) gene was constructed. This contig may contain as much as 690 kb of DNA from the alpha 5(IV) locus. On the basis of the information obtained from these YAC clones, the genomic map and gene structure of the alpha 5(IV) gene have been refined. This study has also provided a valuable resource for subsequent studies of the alpha 5(IV) gene and its flanking DNA sequences.     

Effect of glycine substitutions on alpha5(IV) chain structure and structure-phenotype correlations in Alport syndrome

The phenotype variety caused by glycine substitutions in alpha5(IV) chain in X-linked Alport syndrome (XLAS) prompted the complexity of structure changes of alpha5(IV) chain that was little to know now. In this study, we expressed a domain of alpha5(IV) chain containing different glycine substitutions (G1015V and G1030S, respectively) which were revealed in two XLAS pedigrees with different phenotype severities and the corresponding domain of a control in Escherichia coli. The recombinant proteins were characterized by immunoblot and mass spectrometry and analyzed the secondary structure by using circular dichroism (CD) spectroscopy. CD analysis showed that the recombinant protein containing G1015V mutation identified in the pedigree of juvenile-onset XLAS exhibited 12.9% alpha-helix that was not found in the control recombinant protein. The spectrum of the recombinant protein containing G1030S mutation identified in the pedigree of adult-onset XLAS was slightly different from that of the control, that is, mostly with the random coil and the beta-sheet, while without alpha-helix. These results demonstrated that two kinds of glycine substitutions, although in the same domain of alpha5(IV) chain, displayed the distinctly different secondary structures. The changes of the secondary structure could explain the phenotypic diversities of XLAS, which would be hardly understood solely by analyzing genomic DNA or mRNA of alpha5(IV) chain.     

Molecular cloning and chromosome assignment of murine N-ras

The murine N-ras gene was cloned by screening an EMBL-3 recombinant phage library with a human N-ras specific probe. Hybridization of two separate unique sequence N-ras probes, isolated from the 5' and 3' flanking sequences of the murine gene, to a mouse-Chinese hamster hybrid mapping panel assigns the N-ras locus to mouse chromosome three.     

Colocalization of the genes for the alpha 3(IV) and alpha 4(IV) chains of type IV collagen to chromosome 2 bands q35-q37.

Each type of basement membrane in man contains between two and five genetically distinct type IV collagens: alpha 1(IV)-alpha 5(IV). Genes for alpha 1(IV), alpha 2(IV), alpha 3(IV), and alpha 5(IV) have been isolated. We have recently isolated partial cDNAs for the fifth member of the family, designated alpha 4(IV). On the basis of comparison of the deduced peptide sequences of all five chains, the type IV collagens can be divided into two families: alpha 1-like, comprising alpha 1(IV), alpha 3(IV), and alpha 5(IV); and alpha 2-like, comprising alpha 2(IV) and alpha 4(IV). Genes encoding the alpha 1(IV) and alpha 2(IV) chains (COL4A1 and COL4A2) both map to human chromosome 13q34 and have been shown to be transcribed from opposite DNA strands using a common bidirectional promoter that allows coordinate regulation of the two chains. Indeed, these two chains are commonly found together in basement membrane and form [alpha 1]2.[alpha 2] heterotrimers. Whereas alpha 1(IV) and alpha 2(IV) have been found in all basement membranes studied hitherto, it has been shown that alpha 3(IV) and alpha 4(IV) are found in only a subset of basement membranes. In basement membranes where either of these molecules is present, however, they are found together. In view of this relationship and the structural similarities between alpha 1(IV) and alpha 3(IV) and between alpha 2(IV) and alpha 4(IV), we hypothesized that COL4A3 and COL4A4, the genes encoding alpha 3(IV) and alpha 4(IV), respectively, have a genomic organization similar to that of COL4A1 and COL4A2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Human collagen gene COL5A1 maps to the q34.2----q34.3 region of chromosome 9, near the locus for nail-patella syndrome.

Type V collagen is a fibrillar collagen that is widely distributed in tissues as a minor component of extracellular matrix and is usually composed of one pro alpha 2 (V) and two pro alpha 1 (V) chains. In this report, recently isolated cDNA and genomic clones, which encode the pro alpha 1 (V) chain, are used as probes for hybridization to filter-bound DNA from a panel of human-mouse hybrid cell lines and for in situ hybridization to metaphase chromosomes. These studies establish the chromosomal location of the COL5A1 gene, which encodes the pro alpha 1 (V) chain, within segment 9q34.2----q34.3. These findings add to the previously characterized dispersion of collagen genes in the human genome, as this is the first example of a collagen locus on chromosome 9. In addition, these studies place COL5A1 near the locus for the genetic disorder, nail-patella syndrome (hereditary osteo-onychodysplasia), which also maps to 9q34.     

Molecular cloning of rat and human type IX collagen cDNA and localization of the alpha 1(IX) gene on the human chromosome 6

Type IX collagen is found in hyaline cartilage, where it is associated with type II collagen in quarter-staggered collagen fibrils. Chicken type IX collagen has been extensively characterized and shown to contain molecules with three triple-helical domains, interspersed with non-triple-helical sequences. The molecule contains three, genetically distinct, subunits and one of these subunits carries a covalently bound glycosaminoglycan side chain. In the present report, we describe for the first time the primary structure of mammalian type IX collagen chains, based on cloning and sequencing of cDNA from rat and human cDNA libraries. The results suggest that mammalian alpha 1(IX) chains have the same multi-domain structure as the avian protein. We also demonstrate, by in situ hybridization of chromosome spreads, that the human alpha 1(IX) collagen gene is located on the long arm of chromosome 6. The cloning of human type IX collagen cDNA provides a probe for molecular studies of human chondrodysplasias that may involve abnormalities in this extracellular collagen-proteoglycan.     

Spectrum of mutations in the COL4A5 collagen gene in X-linked Alport syndrome.

Alport syndrome is a mainly X-linked hereditary disease of basement membranes that is characterized by progressive renal failure, deafness, and ocular lesions. It is associated with mutations of the COL4A5 gene located at Xq22 and encoding the alpha5 chain of type IV collagen. We have screened 48 of the 51 exons of the COL4A5 gene by SSCP analysis and have identified 64 mutations and 10 sequence variants among 131 unrelated Alport syndrome patients. This represents a mutation-detection rate of 50%. There were no hot-spot mutations and no recurrent mutations in our population. The identified mutations were 6 nonsense mutations, 12 frameshift mutations, 17 splice-site mutations, and 29 missense mutations, 27 of the latter being glycine substitutions in the collagenous domain. Two of these occurred on the same allele in one patient and segregated with the disease in the family. We showed that some of the glycine substitutions could be associated with the lack of immunological expression of the alpha3(IV)-alpha5(IV) collagen chains in the glomerular basement membrane.     

Molecular cloning and chromosomal assignment of a human perforin (PFP) gene

Human perforin cDNA was isolated and the complete nucleotide sequence of the gene determined. The deduced amino acid sequence of human perforin showed 68.4% similarity to that of mouse perforin. RNA blot analysis of the human perforin gene revealed that the gene product is expressed preferentially in killer-type cells among cell lines tested, and in large granular lymphocytes among the peripheral blood mononuclear cells. In situ hybridization analysis with a human perforin cDNA probe revealed that the human perforin (PFP) gene is located on chromosome17q11-21. The nucleotide sequence data reported in this paper have been submitted to the GeBank nucleotide sequence database and have been assigned the accession number M28393.