Deletion of complement factor H-related genes CFHR1 and CFHR3 is associated with atypical hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome (aHUS) is associated with defective complement regulation. Disease-associated mutations have been described in the genes encoding the complement regulators complement factor H, membrane cofactor protein, factor B, and factor I. In this study, we show in two independent cohorts of aHUS patients that deletion of two closely related genes, complement factor H-related 1 (CFHR1) and complement factor H-related 3 (CFHR3), increases the risk of aHUS. Amplification analysis and sequencing of genomic DNA of three affected individuals revealed a chromosomal deletion of approximately 84 kb in the RCA gene cluster, resulting in loss of the genes coding for CFHR1 and CFHR3, but leaving the genomic structure of factor H intact. The CFHR1 and CFHR3 genes are flanked by long homologous repeats with long interspersed nuclear elements (retrotransposons) and we suggest that nonallelic homologous recombination between these repeats results in the loss of the two genes. Impaired protection of erythrocytes from complement activation is observed in the serum of aHUS patients deficient in CFHR1 and CFHR3, thus suggesting a regulatory role for CFHR1 and CFHR3 in complement activation. The identification of CFHR1/CFHR3 deficiency in aHUS patients may lead to the design of new diagnostic approaches, such as enhanced testing for these genes.

Deletion of TRPC4 and TRPC6 in Mice Impairs Smooth Muscle Contraction and Intestinal Motility In Vivo.

BACKGROUND & AIMS: Downstream effects of muscarinic receptor stimulation in intestinal smooth muscle include contraction and intestinal transit. We thought to determine whether classic transient receptor potential (TRPC) channels integrate the intracellular signaling cascades evoked by the stimulated receptors and thereby contribute to the control of the membrane potential, Ca-influx, and cell responses. METHODS: We created trpc4-, trpc6-, and trpc4/trpc6-gene-deficient mice and analyzed them for intestinal smooth muscle function in vitro and in vivo. RESULTS: In intestinal smooth muscle cells TRPC4 forms a 55 pS cation channel and underlies more than 80% of the muscarinic receptor-induced cation current (mI(CAT)). The residual mI(CAT) depends on the expression of TRPC6, indicating that TRPC6 and TRPC4 determine mI(CAT) channel activity independent of other channel subunits. In TRPC4-deficient ileal myocytes the carbachol-induced membrane depolarizations are diminished greatly and the atropine-sensitive contraction elicited by acetylcholine release from excitatory motor neurons is reduced greatly. Additional deletion of TRPC6 aggravates these effects. Intestinal transit is slowed down in mice lacking TRPC4 and TRPC6. CONCLUSIONS: In intestinal smooth muscle cells TRPC4 and TRPC6 channels are gated by muscarinic receptors and are responsible for mI(CAT). They couple muscarinic receptors to depolarization of intestinal smooth muscle cells and voltage-activated Ca(2+)-influx and contraction, and thereby accelerate small intestinal motility in vivo.

Deletion of Irs2 causes reduced kidney size in mice: role for inhibition of GSK3 beta?

Background: Male Irs2(-/-) mice develop fatal type 2 diabetes at 13-14 weeks. Defects in neuronal proliferation, pituitary development and photoreceptor cell survival manifest in Irs2(-/-) mice. We identify retarded renal growth in male and female Irs2(-/-) mice, independent of diabetes.

Murine model of autosomal dominant retinitis pigmentosa generated by targeted deletion at codon 307 of the rds-peripherin gene

We introduced a targeted single base deletion at codon 307 of the rds-peripherin gene in mice, similar mutations being known to cause autosomal dominant retinitis pigmentosa (RP) in man. Histopathological and electroretinographic analysis indicate that the retinopathy in mice homozygous for the codon 307 mutation appears more rapid than that in the naturally occurring null mutant, the rds(-/-) mouse, suggesting that the rds-307 mutation displays a dominant negative phenotype in combination with that due to haplosufficiency. RP is the most prevalent cause of registered visual handicap in those of working age in developed countries, the 50 or so mutations so far identified within the RDS-peripherin gene accounting for up to 10% of dominant cases of the disease. Given the sequence homologies that exist between the murine rds-peripherin and the human RDS-peripherin gene, this disease model, the first to be generated for peripherin-based RP using gene targeting techniques, should in principle be of value in the work-up in mice of therapeutics capable of targeting transcripts derived from the human gene.

Delineation of a recognisable phenotype of interstitial deletion 3 (q22.3q25.1) in a case with previously unreported truncus arteriosus

Interstitial deletions of chromosome 3q22.3e25.1 are very rare with only five previous reports of deletions in this region [1,2,4,7,9]. We describe a case of a female infant with a de novo deletion. Dysmorphic features and congenital heart disease led to a clinical genetics assessment on day 1 of life. Chromosomal analysis showed an interstitial deletion with a female karyotype 46,XX,del (3)(q23q25.1) dn. Subsequent array CGH demonstrated the breakpoints as 3q22.3q25.1. This is the first documented association with a truncus arteriosus. We identify an emerging clinical phenotype of microphthalmia, microcephaly, congenital heart disease, slow feeding, skeletal abnormalities, with an abnormal facies and developmental delay. Array CGH demonstrated that the FOXL2 gene responsible for BPES was not deleted in this patient. (C) 2010 Elsevier Masson SAS. All rights reserved.

The schizophrenia phenotype in 22q11 deletion syndrome

Objective: This study investigated the schizophrenia phenotype in 24 subjects with 22q11 deletion syndrome (22qDS) and schizophrenia (22qDS-schizophrenia), a rare but relatively homogenous genetic subtype of schizophrenia associated with a microdeletion on chromosome 22. Individuals with 22qDS are at genetically high risk for schizophrenia.