Alessandra M.V. Duncan

Cone-rod dystrophy due to mutations in a novel photoreceptor-specific homeobox gene (CRX) essential for maintenance of the photoreceptor

Genes associated with inherited retinal degeneration have been found to encode proteins required for phototransduction, metabolism, or structural support of photoreceptors. Here we show that mutations in a novel photoreceptor-specific homeodomain transcription factor gene (CRX) cause an autosomal dominant form of cone-rod dystrophy (adCRD) at the CORD2 locus on chromosome 19q13. In affected members of a CORD2-linked family, the highly conserved glutamic acid at the first position of the recognition helix is replaced by alanine (E80A). In another CRD family, a 1 bp deletion (E168 [delta1 bp]) within a novel sequence, the WSP motif, predicts truncation of the C-terminal 132 residues of CRX. Mutations in the CRX gene cause adCRD either by haploinsufficiency or by a dominant negative effect and demonstrate that CRX is essential for the maintenance of mammalian photoreceptors.

Isolation and characterization of an α-satellite repeated sequence from human chromosome 22

We constructed a library in λIL47.1 with DNA isolated from flow-sorted human chromosome 22. Over 50% of the recombinants contained the same highly repetitive sequence. When this sequence was used to probe Southern blots of EcoRI-digested genomic DNA, a ladder of bands with increments of about 170 bp was observed. This sequence comigrates with satellite III in Ag+/Cs2SO4 gradients and may account for at least part of the 170 bp Hae III ladder seen in isolated satellite III DNA. Partial sequence analysis revealed homology to the 171 bp monomeric repeat unit of α-R1-DNA and the X specific α-satellite consensus sequence. After low stringency in situ hybridization, silver grains were found over the centromeres of a number of chromosomes. Under high stringency conditions, however, the labeling was concentrated over the centromeric region of chromosome 22. This localization was confirmed using DNA from a panel of human/hamster cell lines which showed that the homologous 2.1 and 2.8 kb EcoR1 restriction fragments were chromosome 22 specific. These clones therefore contain chromosome 22 derived α-satellite sequences analogous to other chromosome-specific satellite sequences described previously.

Pallister‐Killian syndrome: A mild case diagnosed by fluorescence in situ hybridization. Review of the literature and expansion of the phenotype

Pallister-Killian syndrome (PKS) is a rare disorder characterized by a specific combination of anomalies, mental retardation and mosaic presence of a supernumerary isochromosome 12p which is tissue-limited. We report an atypical case of PKS with a mild phenotype. Flourescence in situ hybridization (FISH) was used to demonstrate that the supernumerary marker chromosome identified in the patients fibroblasts was an isochromosome 12p. This study broadens the spectrum of PKS phenotype. It also illustrates the usefulness of fluorescence in situ hybridization in diagnosis of patients with chromosomal abnormalities and mild or atypical clinical findings.

Chromosomal localization of the human prostanoid receptor gene family

Prostaglandins (PGD2, PGE2, PGF2 alpha, and PGI2) and thromboxane A2 (TXA2) are biologically active molecules derived from the metabolism of arachidonic acid by cyclooxygenases. They produce a wide variety of physiological and pathophysiological effects mediated through specific G protein-coupled cell surface receptors. In this study, we have mapped the chromosomal positions of the human genes that encode the PGE2 receptor subtypes (PTGER1, PTGER2, and PTGER3), the PGF2 alpha receptor (PTGFR), the PGI2 receptor (PTGIR), and the TXA2 receptor (TBXA2R) using in situ hybridization. The PTGER1, TBXA2R, and PTGIR genes mapped to chromosome 19 at positions 19p13.1, 19p13.3, and 19q13.3, respectively. The PTGFR and PTGER3 genes mapped to chromosome 1 at positions 1p31.1 and 1p31.2, respectively, and PTGER2 gene mapped to chromosome band 5p13.1.

3-Hydroxy-3-methylglutaryl coenzyme A lyase (HL): cloning and characterization of a mouse liver HL cDNA and subchromosomal mapping of the human and mouse HL genes

Abstract3-Hydroxy-3-methylglutaryl coenzyme A lyase (HL) is a homodimeric mitochondrial matrix enzyme that catalyzes the last step of ketogenesis. Using a human HL cDNA as a probe, we isolated a 1.4-kb mouse HL cDNA (HLM) from a mouse liver library and extended the sequence in the 5′ direction, using RACE PCR to include the complete coding sequence. The nucleotide sequence of the mouse HL coding region is 85.7% identical to human HL, and 52.6% to Ps. mevalonii HL. Peptide identities of 87.4% and 54.3% respectively were observed. Southern analysis of 29 strains of laboratory mice and of Mus spretus revealed a total of about 25 kb of hybridizing fragments and three polymorphic fragments in both EcoRI and HindIII digestions. The mouse HL locus (Hmgcl) was localized on Chromosome (Chr) 4: Pmv-19-12.6±3.6 cM-Hmgcl-7.3±2.3 cM-Xmv-8-1.5±1.0 cM-Gpd1. The human HL locus (HMGCL) was mapped to distal Chr 1p by analysis of a human-hamster hybrid cell panel and by in situ hybridization.

Trisomy 22 in a newborn with multiple malformations

SummaryA case of complete trisomy 22 in live-born female child with multiple malformations is reported. The karyotype of the index patient had 46 chromosomes, with one chromosome 22 missing and one supranumerary metacentric chromosome. Different banding methods and in situ hybridization revealed that the extra chromosome consists of the long arms and a part of the short arms of two chromosomes 22. Our report supplies further proof that a fetus with complete trisomy 22 can occasionally survive to term, but the condition is not compatible with life over a long period.

The frequency and distribution of apoptosis induced by three non-carcinogenic agents in mouse colonic crypts

The appearance of apoptotic cells has been used as an index of carcinogen-induced damage inflicted on the colonic epithelium. We report here that 3 potent biological toxins, colchicine, puromycin and diphtheria toxin which have not been shown to be carcinogenic cause a dose-related increase in apoptotic cells in the colonic epithelium of the mouse. The distribution of apoptosis along the crypt length is characteristic for each of the agents studied.

A widely distributed putative mammalian transcriptional regulator containing multiple paired amphipathic helices, with similarity to yeast SIN3

The mammalian Sin3 gene (mSin3) encodes four paired amphipathic helix (PAH) motifs, three of which and an extended region beyond PAH3 share between 59 and 70% sequence similarity with the yeast transcriptional regulator, SIN3. However, mSin3/SIN3 fusion proteins were not able to substitute for the yeast molecule in complementation assays. Transcripts encoding this putative transcriptional regulator, which maps to human chromosome 15q24, were detected in multiple mouse tissues, with highest levels seen in testis, lung, and thymus. Its wide tissue distribution suggests that mSin3, like yeast SIN3, may regulate the transcription of multiple genes.

Re-evaluation of the sublocalization of esterase D and its relation to the retinoblastoma locus by in situ hybridization

In situ hybridization of a cDNA probe for the esterase D gene (ESD) was carried out on human chromosomes. The probe hybridized most strongly to 13q14.2 and 13q14.3. This observation raises doubts concerning the most recently published assignment of ESD to 13q14.1. A deletion in an individual with retinoblastoma was reported to separate the closely linked ESD and retinoblastoma (RB1) loci, placing ESD proximal to RB1. Quantitative in situ hybridization studies of this deletion do not confirm this interpretation. Rather, they suggest that ESD is missing from the deleted chromosome 13 and duplicated on the normal homolog. From these findings, we conclude that the deletion in this individual cannot be used to determine the orientation nor the sublocalization of ESD and RB1 within the 13q14 region.

Neurofibromatosis in a man with a ring 22: in situ hybridization studies.

In situ hybridization with a c-sis probe was performed on peripheral lymphocytes of a man with neurofibromatosis and a ring 22 chromosome. Hybridization was observed on both the normal #22 and the ring 22, indicating that the patient is not constitutionally hemizygous for c-sis. The implications of a ring 22 constitution and the neurofibromatosis phenotype are discussed.