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.     

Mutagenicity and disinfection by-products in surface drinking water disinfected with peracetic acid

The aims of this research were to study the influence of peracetic acid (PAA) on the formation of mutagens in surface waters used for human consumption and to assess its potential application for the disinfection of drinking water. The results obtained using PAA were compared to those found with sodium hypochlorite (NaClO) and chlorine dioxide (ClO2). The Ames test, root anaphase aberration assay, and root/micronuclei assay in Allium cepa and Tradescantia/micronuclei test were used to evaluate the mutagenicity of disinfected samples. Microbiological tests were also performed, and disinfection by-products (DBPs) were identified using gas chromatography/mass spectrometry (GC/MS). A slight bacterial mutagenicity was found in raw lake and river water, and similar activity was detected in disinfected samples. A plant test revealed genotoxicity in raw river water, and microbiological analysis showed that PAA has bactericidal activity but lower than that of the other disinfectants. The DBPs produced by PAA were mainly carboxylic acids, which are not recognized as mutagenic, whereas the waters treated with the other disinfectants showed the presence of mutagenic/carcinogenic halogenated DBPs. However, additional experiments should be performed with higher concentrations of PAA and using water with higher organic carbon content to better evaluate this disinfectant.     

Nerve growth factor and eosinophils in inflamed juvenile conjunctival nevus

PURPOSE: To study both systemic and ocular nerve growth factor (NGF) in inflamed juvenile conjunctival nevus (IJCN), a benign, inflammatory juxtalimbal lesion characterized by many intralesional eosinophils, and to investigate the behavior of eosinophils cocultured on lesional and extralesional fibroblasts obtained from IJCN biopsies, in relation to NGF. METHODS: Eight patients with IJCN (7-15 years old) and six with noninflamed conjunctival compound nevus (12-30 years old) participated in the study. Conjunctival biopsy specimens were used for routine histology, immunohistochemistry (NGF, trkA, eosinophil cationic protein, and tryptase determination), in situ hybridization (NGF mRNA), and determination of fibroblast growth. Blood of patients with IJCN was used to measure NGF levels (by ELISA) and to isolate eosinophils (magnet activated cell sorter [MACS]). Eosinophils were seeded on lesional and extralesional fibroblasts and their adherence, survival (by trypan blue staining), and functional activity (by eosinophil peroxidase [EPO] assay) were assessed after 4 days. RESULTS: NGF in the blood of patients with IJCN and eosinophils and mast cells in their conjunctivas, were significantly elevated. NGF protein, NGF mRNA, and trkA were found to be increased in IJCN biopsy specimens compared with noninflamed compound nevi. Some NGF and trkA colocalized with eosinophils and mast cells. Lesional fibroblasts produced high amounts of NGF in comparison with extralesional fibroblasts and significantly enhanced eosinophil adherence, without influencing either their viability or activation. Adherence and EPO release were increased, in both lesional and extralesional fibroblasts. CONCLUSIONS: The triggering factors that lead to the prominent inflammation in IJCN are unknown. The data in the current study, showing the presence of increased NG-trkA, eosinophils, and mast cells in IJCN and the modulation of eosinophil properties by lesional fibroblasts partly through NGF, suggest a possible association between IJCN and allergic inflammation. Alternatively, this process may represent a direct immune response induced by the nevus itself.     

Differential levels of soluble intercellular adhesion molecule-1 (sICAM-1) in early breast cancer and benign breast lesions

To date, no soluble markers can discriminate benign from malignant breast lesion; therefore, to assess the diagnostic potential of circulating intercellular adhesion molecule-1 (sICAM-1), serum concentrations of sICAM-1 were quantitated in 230 consecutive patients that underwent surgery for breast neoplasias, utilizing an enzyme-linked immunosorbent assay. Histological diagnosis revealed that 177 patients had breast cancer and 53 had a benign breast disease. In the cancer patient group, 90 subjects had pTl tumors without (pT1N0M0, n=46) or with (pT1N1M0, n=41; pT1N2M0, n=3) regional lymph node metastases. Mean levels of serum sICAM-1 of patients with pT1 breast cancer, without or with regional lymph node involvement, were significantly (P<0.05) higher than those of patients with benign breast lesions and of 49 age-matched control subjects. Elevated levels of serum sICAM-1 were detected in 27/90 (30%) pTl breast tumors and in 1/53 (2%) benign breast lesions; thus, among subjects with high levels of sICAM-1, 96% had breast cancer. No significant correlation was found between levels of serum sICAM-1 and breast cancer progression. These observations, altogether, suggest that in the presence of a suspicious breast neoplasm the quantitative analysis of serum sICAM-1 can orient clinical diagnosis towards malignancy.     

Three Rett patients with both MECP2 mutation and 15q11-13 rearrangements

Autism and Rett syndrome, a severe neurological disorder with autistic behavior, are classified as separate disorders on clinical and etiological ground. Rett syndrome is a monogenic X-linked dominant condition due to de novo mutations in the MECP2 gene, whereas autism is a neurodevelopmental and behavioral disorder with complex genetic basis. Maternally inherited duplications on 15q11-q13 are found in a fraction of autistic children suggesting that an abnormal dosage of gene(s) within this region might cause susceptibility to autism. Now we show that three Rett patients are carriers of both a MECP2 mutation and a 15q11-q13 rearrangement, suggesting that there might be a relationship between autism-related genes and the MECP2 gene.     

Real-time quantitative PCR as a routine method for screening large rearrangements in Rett syndrome: Report of one case of MECP2 deletion and one case of MECP2 duplication

Mutations in the X-linked methyl-CpG-binding protein 2 gene (MECP2) are found in 70-80% of cases of classical Rett syndrome (RTT) and in about 50% of cases of preserved speech variant (PSV). This high percentage of MECP2 mutations, especially in classical RTT cases, suggests that another major RTT locus is unlikely. Missed mutations may be due to the limited sensitivity of the methodology used for mutation scanning and/or the presence of intronic mutations. In a double-copy gene, such as MECP2 in females, current methodologies (e.g., DGGE, SSCP, DHPLC, direct sequencing) are prone to miss gross rearrangements. Three previous reports during 2001-2003 have shown the presence of large deletions in a fraction of MECP2-negative classical RTT patients. We developed a reliable, single tube, quantitative PCR assay for rapid determination of MECP2 gene dosage. This method involves a multiplex reaction using a FAM labeled TaqMan probe with a TAMRA quencher derived from MECP2 exon 4 and two primers derived from the same exon and RNAaseP as an internal reference. The copy number of the MECP2 gene was determined by the comparative threshold cycle method (ddCt). Each sample was run in quadruplicate. We validated this assay through the analysis of 30 healthy controls (15 female and 15 male) and we then applied this method to eight classical RTT and six PSV patients, all negative for MECP2 mutations. We identified gross rearrangements in two patients: a deletion in a classical RTT patient and a duplication in a PSV patient. Our results confirm that a fraction of MECP2-negative RTT cases have MECP2 gross rearrangements and we propose real-time quantitative PCR as a simple and reliable method for routine screening of MECP2 in addition to DHPLC analysis.     

Evidence for genetic modifiers of postnatal lethality in PWS-IC deletion mice

Prader-Willi syndrome (PWS), most notably characterized by infantile hypotonia, short stature and morbid obesity, results from deficiencies in multiple genes that are subject to genomic imprinting. The usefulness of current mouse models of PWS has been limited by postnatal lethality in affected mice. Here, we report the survival of the PWS-imprinting center (IC) deletion mice on a variety of strain backgrounds. Expression analyses of the genes affected in the PWS region suggest that while there is low-level expression from both parental alleles in PWS-IC deletion pups, this expression does not explain their survival on certain strain backgrounds. Rather, the data provide evidence for strain-specific modifier genes that support the survival of PWS-IC deletion mice.     

The H19 methylation imprint is erased and re-established differentially on the parental alleles during male germ cell development

Differences in DNA methylation distinguish the maternal and paternal alleles of many imprinted genes. Allele-specific methylation that is inherited from the gametes and maintained throughout development has been proposed as a candidate imprinting mark. To determine how methylation is established in the germline, we have analyzed the allelic methylation patterns of the maternally expressed, paternally methylated H19 gene during gametogenesis in the mouse embryo. We show here that both parental alleles are devoid of methylation in male and female mid-gestation embryonic germ cells, suggesting that methylation imprints are erased in the germ cells prior to this time. In addition, we demonstrate that the subsequent hypermethylation of the paternal and maternal alleles in the male germline occurs at different times. Although the paternal allele becomes hypermethylated during fetal stages, methylation of the maternal allele begins during perinatal stages and continues postnatally through the onset of meiosis. The differential acquisition of methylation on the parental H19 alleles during gametogenesis implies that the two unmethylated alleles can still be distinguished from each other. Thus, in the absence of DNA methylation, other epigenetic mechanism(s) appear to maintain parental identity at the H19 locus during male germ cell development.