Biomedical subjects

Cynthia C Morton

Publications and source records attributed to Cynthia C Morton.

44 records · Page 3Linked to original sources

PubMed2002

Unrepaired DNA breaks in p53-deficient cells lead to oncogenic gene amplification subsequent to translocations.

Amplification of large genomic regions associated with complex translocations (complicons) is a basis for tumor progression and drug resistance. We show that pro-B lymphomas in mice deficient for both p53 and nonhomologous end-joining (NHEJ) contain complicons that coamplify c-myc (chromosome 15) and IgH (chromosome 12) sequences. While all carry a translocated (12;15) chromosome, coamplified sequences are located within a separate complicon that often involves a third chromosome. Complicon formation is initiated by recombination of RAG1/2-catalyzed IgH locus double-strand breaks with sequences downstream of c-myc, generating a dicentric (15;12) chromosome as an amplification intermediate. This recombination event employs a microhomology-based end-joining repair pathway, as opposed to classic NHEJ or homologous recombination. These findings suggest a general model for oncogenic complicon formation.

Animals↗

PubMed2002

Vascular defects and sensorineural deafness in a mouse model of Norrie disease.

Norrie disease is an X-linked recessive syndrome of blindness, deafness, and mental retardation. A knock-out mouse model with an Ndp gene disruption was studied. We examined the hearing phenotype, including audiological, histological, and vascular evaluations. As is seen in humans, the mice had progressive hearing loss leading to profound deafness. The primary lesion was localized to the stria vascularis, which houses the main vasculature of the cochlea. Fluorescent dyes showed an abnormal vasculature in this region and eventual loss of two-thirds of the vessels. We propose that one of the principal functions of norrin in the ear is to regulate the interaction of the cochlea with its vasculature.

Acoustic Stimulation↗

PubMed2002

Genetics, genomics and gene discovery in the auditory system.

The sounds of silence have forever been broken as genetics and genomics approaches in human and model organisms have provided a powerful and rapid entry into gene discovery in the auditory system. An understanding of the complexities and beauty of the biological process of hearing itself is unfolding as genes underlying hereditary hearing impairment are identified. Genes involved in modifying hearing are also being found, and will be critical to a full comprehension of genotype-phenotype relationships. Investigations in the auditory system will provide important insight into how the nervous system decodes molecular information. Deafness represents a common sensory disorder that can interfere dramatically in the acquisition of speech and language in children, and in the quality of life for a growing aged population. As newborn screening for hearing impairment is being implemented in many birth hospitals, the prospects for precise clinical diagnosis, appropriate genetic counseling and proper medical management for auditory disorders has never been at a more exciting crossroad.

Animals↗

PubMed2002

Psoriasin expression in mammary epithelial cells in vitro and in vivo.

We determined, by serial analysis of gene expression (SAGE) analysis of normal and DCIS (ductal carcinoma in situ) mammary epithelial cells, that psoriasin and several other genes implicated in psoriasis are aberrantly expressed in high-grade, comedo DCIS. Real-time PCR, mRNA in situ hybridization, and immunohistochemical analysis of breast carcinomas confirmed that psoriasin is frequently overexpressed in estrogen receptor-negative tumors. To gain insight into regulatory pathways that control psoriasin expression, we developed polyclonal and monoclonal antibodies and investigated mechanisms that may account for elevated levels of psoriasin in DCIS. Here, we report that loss of attachment to extracellular matrix, growth factor deprivation, and confluent conditions dramatically up-regulate psoriasin expression in MCF10A mammary epithelial cells. All of these conditions are characteristic of high-grade DCIS and psoriatic skin lesions; therefore, the same mechanisms may be responsible for increased expression of psoriasin in vitro and in vivo.

Amino Acid Sequence↗

PubMed2002

The sequence, expression, and chromosomal localization of a novel polycystic kidney disease 1-like gene, PKD1L1, in human.

Polycystin-1 and polycystin-2 are the products of PKD1 and PKD2, genes that are mutated in most cases of autosomal dominant polycystic kidney disease. Since the first two polycystins were cloned, three new members, polycystin-L, -2L2, and -REJ, have been identified. In this study, we describe a sixth member of the family, polycystin-1L1, encoded by PKD1L1 in human. The full-length cDNA sequence of PKD1L1, determined from human testis cDNA, encodes a 2849-amino-acid protein and 58 exons in a 187-kb genomic region. The deduced amino acid sequence of polycystin-1L1 has significant homology with all known polycystins, but the longest stretches of homology were found with polycystin-1 and -REJ over the 1453- and 932-amino-acid residues, respectively. Polycystin-1L1 is predicted to have two Ig-like PKD, a REJ, a GPS, a LH2/PLAT, a coiled-coil, and 11 putative transmembrane domains. Several rhodopsin-like G-protein-coupled receptor (GPCR) signatures are also found in polycystin-1L1. Dot-blot analysis and RT-PCR revealed that human PKD1L1 is expressed in testis and in fetal and adult heart. In situ hybridization analysis showed that the most abundant and specific expression of Pkd1l1 was found in Leydig cells, a known source of testosterone production, in mouse testis. We have assigned PKD1L1 to the short arm of human chromosome 7 in bands p12--p13 and Pkd1l1 to mouse chromosome 11 in band A2 by fluorescence in situ hybridization. We hypothesize a role for polycystin-1L1 in the heart and in the male reproductive system.

Amino Acid Sequence↗

PubMed2002

Gene discovery in the auditory system: characterization of additional cochlear-expressed sequences.

To identify genes involved in hearing, 8494 expressed sequence tags (ESTs) were generated from a human fetal cochlear cDNA library in two distinct sequencing projects. Analysis of the first set of 4304 ESTs revealed clones representing 517 known human genes, 41 mammalian genes not previously detected in human tissues, 487 ESTs from other human tissues, and 541 cochlear-specific ESTs (http://hearing.bwh.harvard.edu). We now report results of a DNA sequence similarity (BLAST) analysis of an additional 4190 cochlear ESTs and a comparison to the first set. Among the 4190 new cochlear ESTs, 959 known human genes were identified; 594 were found only among the new ESTs and 365 were found among ESTs from both sequencing projects. COL1A2 was the most abundant transcript among both sets of ESTs, followed in order by COL3A1, SPARC, EEFY1A1, and TPTI. An additional 22 human homologs of known nonhuman mammalian genes and 1595 clusters of ESTs, of which 333 are cochlear-specific, were identified among the new cochlear ESTs. Map positions were determined for 373 of the new cochlear ESTs and revealed 318 additional loci. Forty-nine of the mapped ESTs are located within the genetic interval of 23 deafness loci. Reanalysis of unassigned ESTs from the prior study revealed 338 additional known human genes. The total number of known human genes identified from 8494 cochlear ESTs is 1449 and is represented by 4040 ESTs. Among the known human genes are 14 deafness-associated genes, including GJB2 (connexin 26) and KVLQT1. The total number of nonhuman mammalian genes identified is 43 and is represented by 58 ESTs. The total number of ESTs without sequence similarity to known genes is 4055. Of these, 778 also do not have sequence similarity to any other ESTs, are categorized into 700 clusters, and may represent genes uniquely or preferentially expressed in the cochlea. Identification of additional known genes, ESTs, and cochlear-specific ESTs provides new candidate genes for both syndromic and nonsyndromic deafness disorders.

Auditory Pathways↗

PubMed2002

PCOLCE deletion and expression analyses in uterine leiomyomata.

Uterine leiomyomata (UL) are benign tumors affecting many women of reproductive age. Cytogenetic studies have indicated that a significant percentage of leiomyomata have chromosomal rearrangements, including those involving the long arm of chromosome 7. Several candidate genes that map to chromosome 7 have been studied for possible roles in the pathogenesis of these tumors. PCOLCE, a gene whose product is involved in the cleavage of type I procollagen C-propeptide, has been mapped to the critical interval on chromosome 7, band q22. Here we evaluate by reverse-transcriptase polymerase chain reaction (RT-PCR) and fluorescence in situ hybridization the expression and deletion status of PCOLCE in a series of karyotyped uterine leiomyomata.

Extracellular Matrix Proteins↗

PubMed2002

Continuing to break the sound barrier: genes in hearing.

The past year has seen major advances in our understanding of the genes involved in Usher syndrome, as well as the discovery of a myriad of other genes expressed specifically in hair cells. Mouse models continue to be invaluable in illuminating our knowledge of how mutations in genes lead to deafness. The role of mitochondrial genes in the hearing process has also contributed to elucidating the workings of the auditory system.

Animals↗