Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q00604 (X-linked)
 16,883 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Alport syndrome (AS) is a genetically heterogeneous renal hereditary disease. Male-to-male transmission has been considered fully indicative of autosomal dominant AS. We report a family with male-to-male transmission of X-linked AS due to an extra X chromosome of paternal origin in the proband. Linkage analysis excluded the autosomal loci and demonstrated segregation with the COL4A5 locus (Xq22.3). Sperm FISH analysis from his father detected an increased XY disomy. Mutation screening of the COL4A5 gene identified a splicing mutation, c.4688G>A. The proband and his paternal grandmother showed random X chromosome inactivation. However, a preferential expression of the aberrantly spliced transcript was detected in the proband when compared to his grandmother. This finding could explain why the AS phenotype of this 47,XXY boy resembles more an affected male than a female carrier. This is the first reported case of concurrence of Alport and Klinefelter syndromes.
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PMID:Male-to-male transmission of X-linked Alport syndrome in a boy with a 47,XXY karyotype. 1595 1

The X-linked form of Alport syndrome (AS) is caused by mutation in the COL4A5 gene located at Xq22.3 and encoding the alpha5-chain of type IV-collagen. More than 400 different mutations have so far been detected in the COL4A5 gene. Not all mutations, however, will be detected using an exon-by-exon mutation detection strategy such as SSCP analysis or direct sequencing. We have previously reported the results of SSCP analysis of 81 patients suspected of X-linked AS. Genomic DNA from these 81 patients was also analyzed for larger genomic rearrangements, using Southern blotting analysis. Abnormal band patterns were found in three patients, two of which were caused by single base substitutions in the coding region, also detected by the SSCP analysis. Here we report the results of the analysis of a larger structural COL4A5 rearrangement that escaped the SSCP analysis. The rearrangement was found to be an inversion of a 21 Mb fragment of the COL4A5 gene comprising exon 9 through 51 with proximal breakpoint within intron 8 at Xq22.3 and a distal breakpoint 56 kb upstream to the initiation codon in the RAB33A gene at Xq25. The inversion of exon 9 through 51 is expected to result in a truncated or absent alpha5(IV)-chain and has not previously been associated with AS. These findings emphasize the need for a supplement to mutation detection strategies such as SSCP analysis and direct sequencing, in order to detect more complicated structural COL4A5 rearrangements. Larger structural rearrangements constitute 2.3% (1/43) of the mutations in the present material.
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PMID:Alport syndrome caused by inversion of a 21 Mb fragment of the long arm of the X-chromosome comprising exon 9 through 51 of the COL4A5 gene. 1613 87

This study examined how often children with persistent familial hematuria were from families where hematuria segregated with the known genetic locus for the condition known as benign familial hematuria or thin basement membrane nephropathy (TBMN) at COL4A3/COL4A4. Twenty-one unrelated children with persistent familial hematuria as well as their families were studied for segregation of hematuria with haplotypes at the COL4A3/COL4A4 locus for benign familial hematuria and at the COL4A5 locus for X-linked Alport syndrome. Eight families (38%) had hematuria that segregated with COL4A3/COL4A4, and four (19%) had hematuria that segregated with COL4A5. At most, eight of the other nine families could be explained by disease at the COL4A3/COL4A4 locus if de novo mutations, non-penetrant hematuria or coincidental hematuria in unaffected family members was present individually or in combination. This study confirms that persistent familial hematuria is not always linked to COL4A3/COL4A4 (or COL4A5) and suggests the possibility of a further genetic locus for benign familial hematuria. This study also highlights the risk of excluding X-linked Alport syndrome on the basis of the absence of a family history or of kidney failure.
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PMID:Persistent familial hematuria in children and the locus for thin basement membrane nephropathy. 1623 97

Alport syndrome (ATS) is a clinically and genetically heterogeneous progressive nephropathy often associated with deafness and/or ocular lesions. The histological aspect is characterized by thinning, thickening and splitting of the glomerular basement membrane (GBM). Alport syndrome is caused by mutations in COL4A3 gene (type IV collagen, alfa-3 chain), or COL4A4 gene (type IV collagen, alfa-4 chain) or COL4A5 gene (type IV collagen, alfa-5 chain) genes. Alport syndrome accounts for 1-2% of renal failure cases in Europe, and for 2-3% of transplanted patients in United States. This review focuses on the three types of Alport syndrome which differ in the clinical progression and in the mode of inheritance. The common X-linked form is caused by mutations in the COL4A5 gene and it accounts for 85% of cases. The autosomal dominant and the autosomal recessive forms are caused by mutations in either COL4A3 or COL4A4 genes. The autosomal recessive form which is responsible for the 10-15% of Alport cases, has been known since several years. On the contrary, the autosomal dominant form has only recently been identified in some families. Furthermore, this review will focus on the difficulties encountered during the genetic counselling related to the differential diagnosis between Alport syndrome and Thin Basement Membrane Disease (TBMD). We will report direct experiences of our group showing the difficulties to give an exact prognosis and a correct recurrence risk to the family.
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PMID:[Clinical and genetic features of the Alport 'syndromes']. 1626 4

A novel type of hereditary transmission of COL4A5 in a Japanese family with X-linked Alport syndrome was detected through analysis of cDNA sequences and an X-chromosome inactivation assay. A female patient with moderately altered renal function, who was diagnosed with Alport syndrome by renal biopsy, and her mother, who was undergoing maintenance haemodialysis, showed similar tissue-specific expression of a truncated isoform of COL4A5, which was generated by alternative splicing without a splice-site mutation. Expression of the truncated isoform occurred in the renal specimen derived from the patient, but not in specimens from controls. Genomic analysis revealed two point mutations (c.4821 + 121, T>C; c.4822-151_150, ins T) in intron 49 of COL4A5 from the patient. The peripheral blood mononuclear cells of the patient and her mother showed non-random lyonization. While the females showed only renal impairment, an affected male in the same family suffered from severe renal insufficiency, visual defect and hearing disturbances. Hence, we suggest that this type of heredity COL4A5 presents with phenotypic variation in female heterozygous X-linked Alport syndrome patients.
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PMID:Tissue-specific distribution of an alternatively spliced COL4A5 isoform and non-random X chromosome inactivation reflect phenotypic variation in heterozygous X-linked Alport syndrome. 1651 70

Alport syndrome (AS) is a hereditary glomerulonephritis variably associated with neural hearing loss and ocular abnormalities. The prevalence of the disease is estimated at approximately 1 in 50,000 live births. AS arises from mutations in genes encoding alpha chains constituting type IV collagen. In 85% of patients, the disease results from mutations in the COL4A5 gene located on X chromosome. In the hemizygous male, persistent microhematuria is present from early life, then proteinuria and renal insufficiency occur with time, leading to end-stage renal failure before age 40. In the heterozygous female, clinical manifestations vary from completely healthy state to end-stage renal failure, most often reached after the age of 40. In 15% of patients, the disease results from mutations in either the COL4A3 or the COL4A4 gene, both located on chromosome 2. When both alleles are mutated (autosomal recessive form), the phenotype is constantly severe, resembling that of the hemizygous male in the X-linked form. In the heterozygous individual, the clinical spectrum vary from the absence of any manifestation to the development of proteinuria - the so-called autosomal-dominant AS -, and even renal insufficiency, sometimes reaching end-stage (after the age of 40) through the most frequently encountered phenotype, i.e. a persistently isolated microhematuria, accounting for the so-called benign familial hematuria (or healthy carrier state). The determinants of the phenotype remain largely unknown, so that it may be risky to predict renal prognosis in the individual with a single COL4A3/A4 mutation and an isolated microhematuria at the time of examination.
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PMID:[From Alport syndrome to benign familial hematuria: clinical and genetic aspect]. 1689 72

About 85% of Alport syndrome is an X-linked semi-dominant condition caused by mutations in the collagen gene, COL4A5. The large size and high GC content of this gene have presented diagnostic laboratories with problems in identifying mutations with greater than about a 50% success rate since the gene was first cloned 16 years ago. An RNA based approach is adopted here for a first pass mutation scanning coupled with more traditional exon-by-exon screening to increase the rate of mutation identification. Twenty-one mutations were identified in twenty-five patients with clear Alport syndrome including four gross deletions, two deep intronic mutations, three frameshifts, three splice site mutations, eight missense mutations and one inframe deletion.
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PMID:A two-tier approach to mutation detection in the COL4A5 gene for Alport syndrome. 1694 80

Alport Syndrome (AS) is an inherited disorder of the glomerular basement membrane (GBM) transmitted as an X-linked dominant form in approximately 80% of patients. This X-linked form is caused by mutations in the collagen type IV alfa 5 gene (COL4A5) located on chromosome X; in the remainder of the cases, the autosomal, mostly recessive form, results from mutations in the collagen type IV alfa 3 gene (COL4A3) or alfa 4 gene (COL4A4) located on the 2q. Diagnostic lesions can be observed by electron microscopy (EM) and are characterized by thinning, thickening and/or splitting of the GBM. Isolated thinning of the GBM is usually associated with isolated microhematuria, a non progressive condition which has often a familial trait. Skin biopsy has also recently emerged to be a valuable alternative for the diagnosis of X-linked AS, because the alfa 5 (COL4A5) chain is also expressed in the epidermal basement membrane. A reliable diagnosis can often be achieved through combined renal and cutaneous immunohistochemical analysis, even in patients with limited clinical signs or atypical histological findings, and/or without suggestive family history. The present case report is an example of such diagnostic dilemma, where these techniques allowed to make a diagnosis despite contradictive clinical and histological features in contrast with a positive family history of renal disease.
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PMID:[Thin basement membrane and Alport syndrome]. 1712 66

Alport syndrome (AS) is genetically heterogeneous. The gene COL4A5 is mutated in the more frequent X-linked dominant form of the disease whereas COL4A3 or COL4A4 are mutated in the autosomal recessive and dominant forms. Diagnosis of AS and determination of the mode of transmission are important because of the differences in prognosis and genetic counselling attached to these different forms. Recently, promising results have been obtained in Col4a3-null mice, an animal model for AS, with different therapeutic trials when administered early in the course of the disease, an additional reason for making early diagnosis of AS in children. Since the identification of the molecular basis of the disease, mutation screening is theoretically the best diagnostic approach, avoiding the use or renal or skin biopsy. However, for many reasons linked to the genetic heterogeneity of the disease, the large size of the three genes and the random distribution of the mutations all along these huge genes, this method is tedious, expensive and time consuming. Moreover, its sensitivity is reduced. For these reasons, evaluation of the expression of type IV collagen chains in the skin, and if necessary in the renal basement membrane, remains a useful tool for AS diagnosis. At this time, the indication for these different approaches, which are not mutually exclusive but complementary, depends on the patient clinical presentation and family history.
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PMID:Diagnosis of Alport syndrome without biopsy? 1594 78

Alport syndrome (ATS) and benign familial hematuria (BFH) are type IV collagen inherited disorders. Mutations in COL4A5 are generally believed to cause X-linked ATS, whereas mutations in COL4A3 and COL4A4 genes can be associated with the autosomal-recessive and -dominant type of ATS or BFH. In view of the wide spectrum of phenotypes, an exact diagnosis is sometimes difficult to achieve. This study involved screening each exon with boundary intronic sequences of COL4A3, COL4A4, and COL4A5 genes by optimized polymerase chain reaction-single-stranded conformational polymorphism analysis in 17 families with ATS and in 40 families diagnosed as having BFH. Twelve different mutations were found in the COL4A5 gene in ATS patients, comprising nine missense mutations, a splice site mutation, a mutation causing frameshift, and a nonsense mutation. One of the missense mutations (p.G624D) was present not only in one family with ATS but also in five families with suspected BFH. Three heterozygous mutations in the COL4A3 gene (two missense and one frameshift) and four heterozygous mutations in COL4A4 (two splice site, one in-frame deletion, and one missense) were identified in patients with BFH. Sixteen mutations are to the best of our knowledge new and private.
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PMID:Sixteen novel mutations identified in COL4A3, COL4A4, and COL4A5 genes in Slovenian families with Alport syndrome and benign familial hematuria. 1739 19


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