Major COL4A5 gene rearrangements in patients with juvenile type Alport syndrome

Intracerebral hemorrhage in a neonate with an intragenic COL4A2 duplication

Intracerebral hemorrhage is rare in term born neonates. Besides several non‐genetic risk factors, pathogenic variants in COL4A1 and COL4A2 have been described to play a role in the pathophysiology of neonatal intracerebral hemorrhage. To the best of our knowledge, no intragenic COL4A2 duplications have been reported in humans to date. We report a neonate with intracerebral hemorrhage and a de novo intragenic COL4A2 duplication. Although it is not clear yet whether this genetic factor fully explains the clinical phenotype, it may have contributed at least as a risk factor for cerebral hemorrhage. Screening for intragenic COL4A1 and COL4A2 duplications as part of collagen IV diagnostics should be considered as part of the fetal and neonatal work‐up for unexplained cerebral hemorrhages and to collect more evidence of the pathogenicity of this genetic mechanism.

MFAP2 is overexpressed in gastric cancer and promotes motility via the MFAP2/integrin α5β1/FAK/ERK pathway

Gastric cancer (GC) is one of the most common malignancies and its prognosis is extremely poor. This study identifies a novel oncogene, microfibrillar-associated protein 2 (MFAP2) in GC. With integrative reanalysis of transcriptomic data, we found MFAP2 as a GC prognosis-related gene. And the aberrant expression of MFAP2 was explored in GC samples. Subsequent experiments indicated that silencing and exogenous MFAP2 could affect motility of cancer cells. The inhibition of silencing MFAP2 could be rescued by another FAK activator, fibronectin. This process is probably through affecting the activation of focal adhesion process via modulating ITGB1 and ITGA5. MFAP2 regulated integrin expression through ERK1/2 activation. Silencing MFAP2 by shRNA inhibited tumorigenicity and metastasis in nude mice. We also revealed that MFAP2 is a novel target of microRNA-29, and miR-29/MFAP2/integrin α5β1/FAK/ERK1/2 could be an important oncogenic pathway in GC progression. In conclusion, our data identified MFAP2 as a novel oncogene in GC and revealed that miR-29/MFAP2/integrin α5β1/FAK/ERK1/2 could be an important oncogenic pathway in GC progression.

Prognostic value of glomerular collagen IV immunofluorescence studies in male patients with X-linked Alport syndrome

BACKGROUND AND OBJECTIVES

X-linked Alport syndrome (X-AS) is caused by mutations of the COL4A5 gene, which encodes for the collagen IV α5 chain (α5[COLIV]), resulting in structural and functional abnormalities of the glomerular basement membrane (GBM) and leading to CKD. The aim of the present study was to evaluate the prognostic value of residual collagen IV chain expression in the GBM of patients with X-AS.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The medical records of 22 patients with X-AS from 21 unrelated families collected between 1987 and 2009 were reviewed (median age at last follow-up, 19.9 years; range, 5.4-35.1 years); GBM expression of α1, α3, and α5(COLIV) chains was assessed by immunofluorescence microscopy.

RESULTS

GBM distribution of the α5(COLIV) chain was diffuse in 1 and segmental or absent in 21 of the 22 patients; the expression of the α3(COLIV) chain was diffuse in 5 of 22 patients and segmental or absent in 17 of 22 patients. Patients with diffuse staining for the α3(COLIV) chain presented with proteinuria significantly later (median age, 16.9 versus 6.1 years; P=0.02) and reached an estimated GFR < 90 ml/min per 1.73 m(2) at an older age (median age, 27.0 versus 14.9 years; P=0.01) compared with patients with segmental or absent staining. Two thirds of patients with abnormal α3(COLIV) expression by immunofluorescence studies had null or truncating COL4A5 mutations, as opposed to none of the 4 tested patients with diffuse α3(COLIV) chain glomerular distribution.

CONCLUSIONS

These results indicate that maintained expression of the α3(COLIV) chain is an early positive prognostic marker in patients with X-linked Alport symdrome.

Twenty-one novel mutations identified in the COL4A5 gene in Chinese patients with X-linked Alport's syndrome confirmed by skin biopsy

BACKGROUND

The clinical and pathological features of Alport syndrome are characterized by abnormalities in the basement membrane collagen network which are composed of the α3, α4 and α5 chains of type IV collagen and usually associated with hearing loss and ocular lesions. The predominant form (85% of AS) is inherited as X-linked mode (XLAS) caused by mutations encoding the α5 chain of type IV collagen gene, COL4A5. Different mutations in the COL4A5 gene have been reported widely, but only a few mutations were identified in Chinese patients.

METHODS

We studied 71 Chinese patients from 35 unrelated families with XLAS confirmed by skin biopsy. Genomic DNA was extracted from peripheral blood of all patients. All 51 exons of the COL4A5 gene were screened by direct sequencing for the probands.

RESULTS

A total of twenty-five identified gene mutations were considered to be pathogenic, including 1 nonsense, 1 splice-site, 1 complex rearrangement, 5 small deletions, 2 small insertions and 15 missense mutations. Twenty-one mutations have not been reported previously.

CONCLUSIONS

We have identified 25 pathogenic mutations in 35 Chinese families with XLAS. Skin biopsy is effective for the diagnosis of XLAS.

MLPA and cDNA analysis improves COL4A5 mutation detection in X-linked Alport syndrome

The X-linked form of Alport syndrome (AS) is caused by mutations in the COL4A5 gene encoding the alpha5 chain of type IV collagen. Most COL4A5 mutations are individual, and mutation analysis is complicated by the size of the gene and the number of exons. Larger structural rearrangements account for 10-15% of mutations. We have established a method for mutation analysis of COL4A5 based on reverse transcriptase-polymerase chain reaction analysis of mRNA from cultured skin fibroblasts and multiplex ligation-dependent probe amplification (MLPA) on genomic DNA. One advantage of using skin biopsies for the mRNA analysis is the possibility of immunohistochemical staining for the alpha5(IV) chain on skin sections to support a diagnosis of X-linked AS. A mutation was detected in all five cases included. One patient presenting with AS and diffuse leiomyomatosis was found to have a COL4A5 deletion extending into and comprising COL4A6 exons 1, 1', and 2. We have evaluated the MLPA assay on samples from 67 previously tested AS patients (45 males and 22 females) and 20 controls. We found that the combination of cDNA and MLPA analysis improves the mutation detection rate in COL4A5 and that MLPA should be the first step in genetic testing for X-linked AS.

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

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.

Thin glomerular basement membrane disease: clinical significance of a morphological diagnosis--a collaborative study of the Italian Renal Immunopathology Group

BACKGROUND

Thin glomerular basement membrane disease (TBMD) is a nephropathy defined by diffuse thinning of the glomerular basement membrane (GBM) at electron microscopy examination, without the alterations of Alport's syndrome (ATS). It is known that many patients with TBMD have a type IV collagen disorder and that the disease occasionally may be progressive. This study investigated 51 patients with the morphological diagnosis of TBMD lacking any sign of ATS, with the aim of defining the prevalence of type IV collagen mutations and the course of the disease.

METHODS

Patients were investigated as follows: (a) clinical picture and family investigation; (b) renal biopsy findings; (c) immunohistochemical study of renal tissue for collagen IV alpha-chains; (d) pedigree reconstruction and molecular investigations in genes encoding type IV collagen chains, when DNA samples were available; and (e) follow-up data.

RESULTS

Renal biopsy analysis revealed no light microscopy changes in 27 patients and minimal abnormalities in the remainder. Global glomerular sclerosis was found in seven cases and superimposed mesangial immunoglobulin-A deposits in four. Normal staining of GBM for alpha(IV) chains was observed in all but one patient, where alpha5(IV) was absent and molecular investigation revealed a COL4A5 mutation. Five out of 25 cases had a mutation in the COL4A3/COL4A4 genes. Eight out of 38 patients followed up for 12-240 months (21%) showed signs of disease progression or hypertension.

CONCLUSIONS

This study confirms that a considerable proportion of patients with TBMD have a type IV collagen disorder and that this lesion is not always benign. Thus, families should be investigated carefully whenever possible and patients and affected relatives should be examined periodically for signs of disease progression.

COL4A3/COL4A4 mutations: from familial hematuria to autosomal-dominant or recessive Alport syndrome

COL4A3/COL4A4 mutations: From familial hematuria to autosomal-dominant or recessive Alport syndrome.

BACKGROUND

Mutations of the type IV collagen COL4A5 gene cause X-linked Alport syndrome (ATS). Mutations of COL4A3 and COL4A4 have been reported both in autosomal-recessive and autosomal-dominant ATS, as well as in benign familial hematuria (BFH). In the latter conditions, however, clinical features are less defined, few mutations have been reported, and other genes and non-genetic factors may be involved.

METHODS

We analyzed 36 ATS patients for COL4A3 and COL4A4 mutations by polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) and direct sequencing. Sporadic patients who had tested negative for COL4A5 mutations were included with typical cases of autosomal recessive ATS to secure a better definition of the phenotype spectrum.

RESULTS

We identified seven previously undescribed COL4A3 mutations: in two genetic compounds and three heterozygotes, and one in COL4A4. In agreement with the literature, some of the mutations of compound heterozygotes were associated with microhematuria in healthy heterozygous relatives. The mutations of heterozygous patients are likely dominant, since no change was identified in the second allele even by sequencing, and they are predicted to result in shortened or abnormal chains with a possible dominant-negative effect. In addition, both genes showed rare variants of unclear pathogenicity, and common polymorphisms that are shared in part with other populations.

CONCLUSIONS

This study extends the mutation spectrum of COL4A3 and COL4A4 genes, and suggests a possible relationship between production of abnormal COL IV chains and dominant expression of a continuous spectrum of phenotypes, from ATS to BFH.

Distribution of alpha-chains of type IV collagen in glomerular basement membranes with ultrastructural alterations suggestive of Alport syndrome

BACKGROUND

In Alport syndrome (AS) impaired production and/or assembly of col IV alpha-chain isoforms results in abnormal structure of glomerular basement membrane (GBM), haematuria and, frequently, progressive renal disease. We investigated the relationship between col IV alpha-chains expression and morphology of GBM, as a possible key to the better understanding of the pathogenesis of renal disease in AS.

METHODS

GBM distribution of col IV alpha1-, alpha3-, and alpha5-chain was investigated by immunohistochemistry in 32 patients (21 males and 11 females, mean age at biopsy of 11.5 years) with ultrastructural findings suggestive of AS. Ten patients had a proven COL4A5 mutation. Based on the severity of ultrastructural findings, the biopsies were grouped in three (I-III) electron microscopy (EM) classes. Significant EM changes of GBM (thinning, thickening, splitting, basket weaving of the lamina densa) were singularly evaluated using a semiquantitative scale (0-3).

RESULTS

Col IV alpha1-chain was demonstrated in GBM of all patients. Three patterns of staining for col IValpha3- and alpha5-chains were observed: positive, negative, and alpha3(IV)-positive/alpha5(IV)-negative. By chi(2)-test, EM class III lesions and complete loss of alpha3(IV)- and alpha5(IV)-antigen were significantly more frequent (P<0.05 and P<0.01) in male patients, but no significant relation was observed between EM classes and immunohistochemical patterns. GBM alterations did not correlate with staining for alpha5(IV)-chain. Intensity of alpha3(IV)-chain staining, however, had a negative correlation (P<0.05) with the severity of GBM basket weaving.

CONCLUSIONS

Our results suggest that the alpha3(IV)-chain-containing col IV-network plays a fundamental role in structural and, possibly, functional organization of GBM. Absence of alpha3(IV)-chain in GBM could indicate a more severe renal disease in AS.

The clinical spectrum of type IV collagen mutations

Clinical manifestations of type IV collagen mutations can vary from the severe, clinically and genetically heterogeneous renal disorder, Alport syndrome, to autosomal dominant familial benign hematuria. The predominant form of Alport syndrome is X-linked; more than 160 different mutations have yet been identified in the type IV collagen alpha 5 chain (COL4A5) gene, located at Xq22-24 head to head to the COL4A6 gene. The autosomal recessive form of Alport syndrome is caused by mutations in the COL4A3 and COL4A4 genes, located at 2q35-37. Recently, the first mutation in the COL4A4 gene was identified in familial benign hematuria. This paper presents an overview of type IV collagen mutations, including eight novel COL4A5 mutations from our own group in patients with Alport syndrome. The spectrum of mutations is broad and provides insight into the clinical heterogeneity of Alport syndrome with respect to age at renal failure and accompanying features such as deafness, leiomyomatosis, and anti-GBM nephritis.

Alport syndrome, mental retardation, midface hypoplasia, and elliptocytosis: a new X linked contiguous gene deletion syndrome?

We describe a family with four members, a mother, two sons, and a daughter, who show clinical features consistent with X linked Alport syndrome. The two males presented with additional features including mental retardation, dysmorphic facies with marked midface hypoplasia, and elliptocytosis. The elliptocytosis was not associated with any detectable abnormalities in red cell membrane proteins; red cell membrane stability and rigidity was normal on ektacytometry. Molecular characterisation suggests a submicroscopic X chromosome deletion encompassing the entire COL4A5 gene. We propose that the additional abnormalities found in the affected males of this family are attributable to deletion or disruption of X linked recessive genes adjacent to the COL4A5 gene and that this constellation of findings may represent a new X linked contiguous gene deletion syndrome.

FACL4, a new gene encoding long-chain acyl-CoA synthetase 4, is deleted in a family with Alport syndrome, elliptocytosis, and mental retardation

We observed a family in which two boys were diagnosed with Alport syndrome, elliptocytosis, and mental retardation and carried a large deletion of the Xq22.3-q23 region, encompassing the COL4A5 gene. This suggests the possibility of a new contiguous gene syndrome. In an attempt to characterize the genes contributing to this complex phenotype, we have isolated a gene encoding a new long-chain acyl-CoA synthetase (FACL4 or LACS4) from the region deleted in these patients. Among several ESTs identified by searching the human gene map database maintained at the National Center for Biotechnology Information, using the map position as a query, only one was deleted in the patients. RACE products containing the entire ORF were subsequently generated. Northern blot analysis showed a 5-kb mRNA expressed in several tissues except for liver and lung. Brain shows a longer transcript, possibly reflecting the use of a brain-specific upstream ATG start codon. FACL4 encodes a predicted protein product of 670 amino acids (711 in brain), with a remarkable level of conservation compared to the rat acyl-CoA synthetases ACS4 and brain-specific ACS3 protein sequences. We are investigating the possibility that the absence of this enzyme may play a role in the development of mental retardation or other signs associated with Alport syndrome in the family.