Dopaminergic cell damage and vulnerability to MPTP in Pink1 knockdown zebrafish

The functions of PTEN (phosphatase/tensin homolog)-induced putative kinase (PINK1), which is mutated in early-onset Parkinson's disease, are poorly understood. We characterized a PINK1 antibody and found colocalization of PINK1-like immunoreactivity with aminergic markers. We inactivated translation of Pink1 using morpholino-oligonucleotides (MOs) in larval zebrafish. Dopaminergic neurons consisted of two sets of neuron populations, marked by complementary expression of two tyrosine hydroxylase genes th1 and th2. Translation inhibition of pink1 resulted in reduction of both th mRNA forms until day 5 or 7, respectively. The affected dopaminergic neurons were in one group expressing th1 and three groups expressing th2. Lack of Pink1 sensitized the fish to subeffective doses of MPTP, which caused a locomotor deficit and facilitated loss of th1 in one diencephalic dopaminergic cell group. Control experiments with pink1 mRNA and control MO suggested that effects with the splice site targeting MO were specific. Distinct groups of dopaminergic neurons are thus sensitive to loss of Pink1. Sensitization of the pink1 morphant fish to MPTP toxicity suggests that genetic factors play a role in toxin-induced Parkinson's disease.

Evaluation of immunofluorescence microscopy and enzyme-linked immunosorbent assay in detection of Cryptosporidium and Giardia infections in asymptomatic dogs

The performance of immunofluorescence microscopy (IF) and enzyme-linked immunosorbent assay (ELISA) in canine feces was evaluated. IF and Cryptosporidium ELISA detected 10(5)oocysts/g, while the detection limit for Giardia ELISA was 10(4)cysts/g. The Cryptosporidium ELISA showed 94% specificity but only 71% sensitivity. The Giardia ELISA correlated well with IF (sensitivity 100%, specificity 96%) and was capable of detecting animal specific Giardia duodenalis genotypes. Visual interpretation appeared appropriate for assessment of ELISA results. The proportion of positive samples and possible zoonotic character of Cryptosporidium and Giardia infections in 150 asymptomatic Finnish dogs from the Helsinki area were studied. The overall proportion of dogs positive for Cryptosporidium was 5% (7/150) and that for Giardia 5% (8/150). In dogs < or =12 months old, the corresponding proportions were 17% and 19% (n=36). Sequence analyses of the 18S rDNA gene identified the isolates as Cryptosporidium canis and animal specific genotypes of G. duodenalis (assemblages C-E), indicating restricted risk of zoonotic transmission.

Delineation of Cohen syndrome following a large-scale genotype-phenotype screen

Cohen syndrome is an autosomal recessive condition associated with developmental delay, facial dysmorphism, pigmentary retinopathy, and neutropenia. The pleiotropic phenotype, combined with insufficient clinical data, often leads to an erroneous diagnosis and has led to confusion in the literature. Here, we report the results of a comprehensive genotype-phenotype study on the largest cohort of patients with Cohen syndrome assembled to date. We found 22 different COH1 mutations, of which 19 are novel, in probands identified by our diagnostic criteria. In addition, we identified another three novel mutations in patients with incomplete clinical data. By contrast, no COH1 mutations were found in patients with a provisional diagnosis of Cohen syndrome who did not fulfill the diagnostic criteria ("Cohen-like" syndrome). This study provides a molecular confirmation of the clinical phenotype associated with Cohen syndrome and provides a basis for laboratory screening that will be valuable in its diagnosis.

Cohen syndrome in the Ohio Amish

We describe eight members from two large Amish kindreds who share a phenotype characterized by early-onset pigmentary retinopathy and myopia, global developmental delay and mental retardation, microcephaly, short stature, hypotonia, joint hyperextensibility, small hands and feet, common facial appearance, and friendly disposition. Several of the children had intermittent granulocytopenia. The phenotypic occurrence in three siblings coupled with the increased coefficient of inbreeding in the Amish suggested that this disorder is autosomal recessive and due to a single founder allele. Despite similarity to the clinical features of Cohen syndrome, experienced dysmorphologists attending the 23rd David W. Smith Workshop suggested the facial gestalt of the Amish children was inconsistent with this diagnosis. We mapped the locus responsible for these individuals' phenotype to chromosome 8q22-q23, which contains the recently discovered Cohen syndrome gene, COH1. Complete sequencing of the COH1 gene identified a likely disease-causing frameshift mutation and a missense mutation in the Amish patients. A comparison of features among different Cohen syndrome populations with shared linkage to the COH1 locus or known COH1 gene mutations may allow for the determination of improved clinical criteria on which to suspect the diagnosis of Cohen syndrome. We conclude that facial gestalt seems to be an unreliable indicator of Cohen syndrome between ethnic populations, although it is quite consistent among affected individuals within a particular ethnic group. Other features common to almost all individuals with proven COH1 mutations, such as retinal dystrophy, myopia, microcephaly, mental retardation, global developmental delay, hypotonia, and joint hyperextensibility appear to be better clinical indicators of this disorder.

Cohen syndrome is caused by mutations in a novel gene, COH1, encoding a transmembrane protein with a presumed role in vesicle-mediated sorting and intracellular protein transport

Cohen syndrome is an uncommon autosomal recessive disorder whose diagnosis is based on the clinical picture of nonprogressive psychomotor retardation and microcephaly, characteristic facial features, retinal dystrophy, and intermittent neutropenia. We have refined the critical region on chromosome 8q22 by haplotype analysis, and we report the characterization of a novel gene, COH1, that is mutated in patients with Cohen syndrome. The longest transcript (14,093 bp) is widely expressed and is transcribed from 62 exons that span a genomic region of approximately 864 kb. COH1 encodes a putative transmembrane protein of 4,022 amino acids, with a complex domain structure. Homology to the Saccharomyces cerevisiae VPS13 protein suggests a role for COH1 in vesicle-mediated sorting and transport of proteins within the cell.

Diagnostic criteria, clinical characteristics, and natural history of Cohen syndrome

Cohen syndrome is a rare, recessively inherited condition associated with facial dysmorphism, developmental delay, and visual disability. A delay in making the diagnosis commonly occurs, contributed to by the lack of a definitive molecular test and the clinical variability of published case reports. A specific clinical phenotype has been delineated in a homogeneous cohort of Finnish Cohen syndrome patients, but the applicability of their diagnostic criteria to non-Finnish patients has been debated. Detailed delineation of Cohen syndrome in patients from outside Finland is therefore warranted. We report on the clinical features of 33 non-Finnish Cohen syndrome patients. Variability within the clinical spectrum is identified and the natural history of Cohen syndrome described. Diagnostic guidelines for facilitating accurate and early diagnosis are discussed. Results from molecular genetic analysis using markers located within the previously mapped COH1 critical region support allelic but not genetic heterogeneity in this UK cohort.

Refined mapping of the Cohen syndrome gene by linkage disequilibrium

The Cohen syndrome is a rare autosomal recessively inherited disorder. Contrary to many case reports published elsewhere, the phenotype is uniform in Finland including nonprogressive mental and motor retardation, typical dysmorphic features, granulocytopenia and marked ophthalmological changes. By linkage analysis in five Finnish multiplex nuclear families, the COH1 locus for the Cohen syndrome was recently assigned to a 10-cM region between loci D8S270 and D8S521 on the long arm of chromosome 8. Here we present results of linkage disequilibrium and haplotype analysis in an extended panel of 16 Finnish COH1 families using new markers localized in the COH1 region. By inferring historical recombinations in conserved haplotypes the COH1 gene was assigned in the region of marker loci D8S1808, D8S1762 and D8S546. Calculations of genetic distances based on linkage disequilibrium suggest that the most likely localization of COH1 is in the immediate vicinity of marker locus D8S1762. Haplotype analysis suggests the occurrence of one main COH1 mutation and possibly one or two rare ones in Finland. This information will be useful in the positional cloning of the gene.

The genetics of cornea plana congenita

Cornea plana congenita is believed to occur in a mild autosomal dominant (CNA1) and a more severe autosomal recessive (CNA2) form. We recently assigned a CNA2 locus to a region on chromosome 12 by linkage analysis. In this study we compared these traits clinically and genetically. Using the horizontal corneal refraction value in diopters (D) as a parameter, a control population (n = 473) had a mean value of 43 center dot 4 (SD 1 center dot 5 D) for men and 43 center dot 7 (SD 1 center dot 6 D) for women, whereas in 51 subjects affected with CNA2 the mean value was 29 center dot 9 (SD 5 center dot 2 D) and in five subjects affected with CNA1 the mean value was 37 center dot 8 (SD 1 center dot 6 D). By linkage analysis in two CNA1 families the CNA2 locus could be conclusively excluded. These data suggest that at least two forms of hereditary cornea plana exist which are both clinically and genetically distinct.

Linkage disequilibrium mapping of the cornea plana congenita gene CNA2

We recently assigned a gene for autosomal recessive cornea plana congenita (CNA2; MIM No. 217300) by linkage analysis to the approximately 3-cM interval between markers D12S82 and D12S327. Here, we extended these studies by exploiting the haplotype and linkage disequilibrium information that can be derived from the genetically isolated Finnish population and its subpopulations. By testing 32 independent families with 10 polymorphic markers in the CNA2 interval, strong allelic association between CNA2 and a set of markers with a peak at marker D12S351 was detected. Based on linkage disequilibrium analysis, the critical region for CNA2 could be narrowed to only 0.04-0.3 cM from marker D12S351, thus defining a critical interval 0.08-0.60 cM in length. These results provide a basis for highly focused positional cloning of CNA2.

A gene for autosomal recessive nemaline myopathy assigned to chromosome 2q by linkage analysis

Clinical genetic evidence suggests the existence of an autosomal recessive form of congenital nemaline myopathy in addition to the autosomal dominant one(s). One mutation in an Australian kindred has been identified as causing an autosomal dominant form of the disease. This mutation in the alpha-tropomyosin gene TPM3 has previously been excluded as causing autosomal recessive nemaline myopathy. We searched systematically for genetic linkage to autosomal recessive nemaline myopathy (NEM2) by studying microsatellite marker alleles in seven multiplex families from Finland, Denmark, Wales, England and The Netherlands. Significant evidence of linkage was found to markers of chromosome 2q, the highest multipoint lod score value being 5.34 for the marker D2S151. Recombinant genotypes in affected individuals demarcate the the region in which the NEM2 gene is likely to reside as a 13 cM region between the markers D2S150 and D2S142. These results confirm the existence of at least one distinctive form of autosomal recessive nemaline myopathy and provide a basis for the identification of its gene.