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R Kucherlapati

Publications and source records attributed to R Kucherlapati.

At least 73 records · Page 4Linked to original sources
PubMed1997

A mouse model of human familial adenomatous polyposis.

In an effort to generate a good mouse model for human colorectal cancer, we generated mice which carry a mutation in the adenomatous polyposis coli (Apc) gene. Mice which are heterozygous for the mutation, designated Apc1638, develop colonic polyps and tumors of the small intestine. Neoplasms were found in 96% of animals studied, and they included adenomas, adenocarcinomas, and polypoid hyperplasias. The mice developed an average of 3.3 tumors, with the highest number in duodenum, followed by jejunum, stomach, ileum, and colon. Focal areas of dysplasias were observed in the colonic mucosa in 50% of mice which were 10 months old or older. These results suggest that mice carrying the Apc1638 mutation can serve as a good model to study the initiation, progression, and inhibition of gastrointestinal tumors.

Adenomatous Polyposis Coli↗
PubMed1997

Retinal pigment epithelium abnormalities in mice with adenomatous polyposis coli gene disruption.

OBJECTIVE: To examine eyes from mice with targeted adenomatous polyposis coli (APC) gene disruption to determine if retinal pigment epithelium (RPE) abnormalities replicate the human counterpart. METHODS: Thirty-two eyes from 16 mice heterozygous for APC gene disruption (chain-termination mutation in codon 1638 of exon 15) and 12 control eyes were examined by light microscopy. RESULTS: Fifteen of 32 eyes from 12 of 16 APC-disrupted mice demonstrated abnormalities of the RPE and retina. The RPE abnormalities included RPE coloboma, unifocal and multifocal RPE hypertrophy, RPE hyperplasia, and RPE duplication with invasion in the areas of outer and inner segments. Retinal abnormalities included outer nuclear layer duplication and outer nuclear layer atrophy. There were no RPE and retinal abnormalities seen in the control eyes. CONCLUSIONS: This study is consistent with the hypothesis that the APC gene is critical in the regulation of RPE proliferation and development. These findings also demonstrate that mutation of the APC gene in codon 1638, a location beyond the previously described critical region for human RPE abnormalities, leads to perturbation in the mouse RPE and retina. Further study of this murine model and the APC/RPE relationship may provide insight into regulatory mechanisms for RPE proliferation.

Adenomatous Polyposis Coli↗
PubMed1997

AICL: a new activation-induced antigen encoded by the human NK gene complex.

The NK gene complex on mouse chromosome 6 and its human homologue on chromosome 12 encode type II transmembrane proteins with a C-type lectin domain which trigger or inhibit target cell lysis by NK cells (NKR-P1, Ly49, NKG2, CD94) or function as cellular activators of various hematopoietic cells (CD69). We herein report the cDNA cloning of a new molecule, designated activation-induced C-type lectin (AICL), whose gene maps to the human NK gene complex proximal to the CD69 gene. AICL is a 149-amino acid (aa) polypeptide with a short cytoplasmic part of seven aa and a C-type lectin domain separated from the transmembrane region by only nine aa. The highest sequence similarity is found to the C-type lectin domains of CD69 and the chicken lectin 17.5. The presence of AICL transcripts in different cell types of hematopoietic origin, a rapid increase of gene transcription during lymphocyte activation, and a short half-life of the mRNA characterize AICL as a new, broadly expressed activation antigen.

Amino Acid Sequence↗
PubMed1997

Mutations in human TBX5 [corrected] cause limb and cardiac malformation in Holt-Oram syndrome.

Holt-Oram syndrome is characterized by upper limb malformations and cardiac septation defects. Here, we demonstrate that mutations in the human TBX5 gene underlie this disorder. TBX5 was cloned from the disease locus on human chromosome 12q24.1 and identified as a member of the T-box transcription factor family. A nonsense mutation in TBX5 causes Holt-Oram syndrome in affected members of one family; a TBX5 missense mutation was identified in affected members of another. We conclude that TBX5 is critical for limb and heart development and suggest that haploinsufficiency of TBX5 causes Holt-Oram syndrome.

Abnormalities, Multiple↗
PubMed1997

Molecular definition of 22q11 deletions in 151 velo-cardio-facial syndrome patients.

Velo-cardio-facial syndrome (VCFS) is a relatively common developmental disorder characterized by craniofacial anomalies and conotruncal heart defects. Many VCFS patients have hemizygous deletions for a part of 22q11, suggesting that haploinsufficiency in this region is responsible for its etiology. Because most cases of VCFS are sporadic, portions of 22q11 may be prone to rearrangement. To understand the molecular basis for chromosomal deletions, we defined the extent of the deletion, by genotyping 151 VCFS patients and performing haplotype analysis on 105, using 15 consecutive polymorphic markers in 22q11. We found that 83% had a deletion and >90% of these had a similar approximately 3 Mb deletion, suggesting that sequences flanking the common breakpoints are susceptible to rearrangement. We found no correlation between the presence or size of the deletion and the phenotype. To further define the chromosomal breakpoints among the VCFS patients, we developed somatic hybrid cell lines from a set of VCFS patients. An 11-kb resolution physical map of a 1,080-kb region that includes deletion breakpoints was constructed, incorporating genes and expressed sequence tags (ESTs) isolated by the hybridization selection method. The ordered markers were used to examine the two separated copies of chromosome 22 in the somatic hybrid cell lines. In some cases, we were able to map the chromosome breakpoints within a single cosmid. A 480-kb critical region for VCFS has been delineated, including the genes for GSCL, CTP, CLTD, HIRA, and TMVCF, as well as a number of novel ordered ESTs.

Abnormalities, Multiple↗
PubMed1997

Loss of Apc and the entire chromosome 18 but absence of mutations at the Ras and Tp53 genes in intestinal tumors from Apc1638N, a mouse model for Apc-driven carcinogenesis.

The Apc1638N mouse carries a targeted mutant allele at the endogenous adenomatous polyposis coli (Apc) gene and represents a unique in vivo model to study intestinal tumor formation and progression. Heterozygous Apc+/Apc1638N mice progressively develop 5-6 adenomas and adenocarcinomas of the small intestine within the first 6 months of life following a histologic sequence similar to that observed in human intestinal tumors. Here, we present the somatic mutation analysis of a total of 57 tumors. The results indicate that in > or = 75% of the lesions tested the wild type copy of the Apc gene is lost and that this LOH event extends to the entire mouse chromosome 18. Unexpectedly, mutations at the K-, N- and H-ras genes have not been found in these tumors. Immunohistochemical analysis of the Apc1638N tumors failed to detect accumulation of the Tp53 protein. Also, no mutations have been found in exons 7 and 8 of the Tp53 gene. These results indicate that, although the genetic inactivation of Apc is involved in the initiating event of the human as well as murine intestinal tumorigenesis, tumor growth and progression follow different mutational pathways in these two species.

Adenocarcinoma↗
PubMed1997

Molecular analysis of velo-cardio-facial syndrome patients with psychiatric disorders.

Velo-cardio-facial syndrome (VCFS) is characterized by conotruncal cardiac defects, cleft palate, learning disabilities, and characteristic facial appearance and is associated with hemizygous deletions within 22q11. A newly recognized clinical feature is the presence of psychiatric illness in children and adults with VCFS. To ascertain the relationship between psychiatric illness, VCFS, and chromosome 22 deletions, we evaluated 26 VCFS patients by clinical and molecular biological methods. The VCFS children and adolescents were found to share a set of psychiatric disorders, including bipolar spectrum disorders and attention-deficit disorder with hyperactivity. The adult patients, >18 years of age, were affected with bipolar spectrum disorders. Four of six adult patients had psychotic symptoms manifested as paranoid and grandiose delusions. Loss-of-heterozygosity analysis of all 26 patients revealed that all but 3 had a large 3-Mb common deletion. One patient had a nested distal deletion and two did not have a detectable deletion. Somatic cell hybrids were developed from the two patients who did not have a detectable deletion within 22q11 and were analyzed with a large number of sequence tagged sites. A deletion was not detected among the two patients at a resolution of 21 kb. There was no correlation between the phenotype and the presence of the deletion within 22q11. The remarkably high prevalence of bipolar spectrum disorders, in association with the congenital anomalies of VCFS and its occurrence among nondeleted VCFS patients, suggest a common genetic etiology.

Abnormalities, Multiple↗
PubMed1996

Characterization of human DSPG3, a small dermatan sulfate proteoglycan.

PG-Lb is a small dermatan sulfate proteoglycan that has been previously characterized in chicken. In the developing limb, chick PG-Lb appears to be exclusively expressed in the zone of flattened chondrocytes. We have cloned and sequenced the human homolog to chick PG-Lb from two human chondrocyte cDNA libraries and a human chondrocyte RNA sample. The human homolog has been named DSPG3, as it is the third member of the small dermatan sulfate proteoglycan family to be identified and characterized along with biglycan (PG-I) and decorin (PG-II). DSPG3 maps to chromosome 12q21 and is composed of 1515 nucleotides of cDNA that code for a 322-amino-acid protein. The protein contains three potential glycosaminoglycan attachment sites, two N-glycosylation sites, a poly- glutamic acid stretch, and six cysteines. By Northern analysis, we have demonstrated that DSPG3 is expressed in cartilage, as well as ligament and placental tissues.

Amino Acid Sequence↗
PubMed1996

Physical mapping of the human neurotensin gene (NTS) between markers D12S1444 and D12S81 on chromosome 12q21.

Neurotensin (NTS) is an endogenous tridecapeptide of the central nervous system and the gastrointestinal tract of different mammalian species including human. The human gene encoding neurotensin has previously been assigned to chromosome 12 but no regional localization was available. We now confirm this assignment and place the NTS gene on the physical and cytogenetic maps. The NTS gene is located on a yeast artificial chromosome contig that contains several polymorphic markers and is close to a polymorphic marker located at 95.8 cM on the Généthon linkage map. NTS is immediately proximal to four polymorphic markers, including D12S81 (AFM102xg9) and D12S88 (AFM158yb4). Using fluorescence in situ hybridization, we map the gene cytogenetically to band 12q21.

Animals↗
PubMed1996

Linkage of asthma and total serum IgE concentration to markers on chromosome 12q: evidence from Afro-Caribbean and Caucasian populations.

To identify genes potentially relevant in atopic asthma, we analyzed markers in chromosome 12q15-q24.1 for linkage to asthma and total serum IgE concentration. Sib-pair analyses of 10 markers in 345 full- and 219 half-sib pairs from 29 multiplex Afro-Caribbean families provided evidence for linkage to this region for both asthma and total serum IgE. Certain alleles at these loci showed significant evidence of transmission disequilibrium with both asthma and high IgE. Using 6 of these markers and 11 additional markers, evidence for linkage of total IgE to 12q was also found in 12 Caucasian Amish kindreds (24 nuclear families) by both sib-pair and transmission disequilibrium analyses. These findings suggest that the 12q15-q24.1 region may contain a gene(s) controlling asthma and the associated "high total IgE" trait.

Adolescent↗
PubMed1996

Association of codon 108/158 catechol-O-methyltransferase gene polymorphism with the psychiatric manifestations of velo-cardio-facial syndrome.

Velo-cardio-facial-syndrome (VCFS) is a common congenital disorder associated with typical facial appearance, cleft palate, cardiac defects, and learning disabilities. The majority of patients have an interstitial deletion on chromosome 22q11. In addition to physical abnormalities, a variety of psychiatric illnesses have been reported in patients with VCFS, including schizophrenia, bipolar disorder, and attention deficit hyperactivity disorder. The psychiatric manifestations of VCFS could be due to haploin-sufficiency of a gene(s) within 22q11. One candidate that has been mapped to this region is catechol-O-methyltransferase (COMT). We recently identified a polymorphism in the COMT gene that leads to a valine-->methionine substitution at amino acid 158 of the membrane-bound form of the enzyme. Homozygosity for COMT158met leads to a 3-4-fold reduction in enzymatic activity, compared with homozygotes for COMT158val. We now report that in a population of patients with VCFS, there is an apparent association between the low-activity allele, COMT158met, and the development of bipolar spectrum disorder, and in particular, a rapid-cycling form.

Abnormalities, Multiple↗
PubMed1996

Physical mapping of a commonly deleted region, the site of a candidate tumor suppressor gene, at 12q22 in human male germ cell tumors.

A candidate tumor suppressor gene (TSG) site at 12q22 characterized by a high frequency of loss of heterozygosity (LOH) and a homozygous deletion has previously been reported in human male germ cell tumors (GCTs). In a detailed deletion mapping analysis of 67 normal-tumor DNAs utilizing 20 polymorphic markers mapped to 12q22-q24, we identified the limits of the minimal region of deletion at 12q22 between D12S377 (proximal) and D12S296 (distal). We have constructed a YAC contig map of a 3-cM region of this band between the proximal marker D12S101 and the distal marker D12S346, which contained the minimal region of deletion in GCTs. The map is composed of 53 overlapping YACs and 3 cosmids onto which 25 polymorphic and nonpolymorphic sequence-tagged sites (STSs) were placed in a unique order. The size of the minimal region of deletion was approximately 2 Mb from overlapping, nonchimeric YACs that spanned the region. We also developed a radiation hybrid (RH) map of the region between D12S101 and D12S346 containing 17 loci. The consensus order developed by RH mapping is in good agreement with the YAC STS-content map order. The RH map estimated the distance between D12S101 and D12S346 to be 246 cR8000 and the minimal region of deletion to be 141 cR8000. In addition, four genes that were previously mapped to 12q22 have been excluded as candidate genes. The leads gained from the deletion mapping and physical maps should expedite the isolation and characterization of the TSG at 12q22.

Chromosomes, Human, Pair 12↗
PubMed1996

cDNA cloning, tissue distribution, and chromosomal localization of myelodysplasia/myeloid leukemia factor 2 (MLF2).

A fusion gene between nucleophosmin (NPM) and myelodysplasia/myeloid leukemia factor 1 (MLF1) is formed by a recurrent t(3;5)(q25.1;q34) in myelodysplastic syndrome and acute myeloid leukemia. Here we report the identification of a novel gene, MLF2, which contains an open reading frame of 744 bp encoding a 248-amino-acid protein highly related to the previously identified MLF1 protein (63% similarity, 40% identity). In contrast to the tissue-restricted expression pattern of MLF1, the MLF2 messenger RNA is expressed ubiquitously. The MLF2 gene locus was mapped by fluorescence in situ hybridization to human chromosome 12p13, a chromosomal region frequently involved in translocations and deletions in acute leukemias of lymphoid or myeloid lineage. In a physical map of chromosome 12, MLF2 was found to reside on the yeast artificial chromosome clone 765b9. Southern blotting analysis of malignant cell DNAs prepared from a series of acute lymphoblastic leukemia cases with translocations involving chromosome arm 12p, as well as a group of acute myeloid leukemias with various cytogenetic abnormalities, failed to reveal MLF2 gene rearrangements.

Amino Acid Sequence↗
PubMed1996

Meiotic pachytene arrest in MLH1-deficient mice.

Germ line mutations in DNA mismatch repair genes including MLH1 cause hereditary nonpolyposis colon cancer. To understand the role of MLH1 in normal growth and development, we generated mice that have a null mutation of this gene. Mice homozygous for this mutation show a replication error phenotype, and extracts of these cells are deficient in mismatch repair activity. Homozygous mutant males show normal mating behavior but have no detectable mature sperm. Examination of meiosis in these males reveals that the cells enter meiotic prophase and arrest at pachytene. Homozygous mutant females have normal estrous cycles and reproductive and mating behavior but are infertile. The phenotypes of the mlh1 mutant mice are distinct from those deficient in msh2 and pms2. The different phenotypes of the three types of mutant mice suggest that these three genes may have independent functions in mammalian meiosis.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Neuronal abnormalities in microtubule-associated protein 1B mutant mice.

Microtubules play an important role in establishing cellular architecture. Neuronal microtubules are considered to have a role in dendrite and axon formation. Different portions of the developing and adult brain microtubules are associated with different microtubule-associated proteins (MAPs). The roles of each of the different MAPs are not well understood. One of these proteins, MAP1B, is expressed in different portions of the brain and has been postulated to have a role in neuronal plasticity and brain development. To ascertain the role of MAP1B, we generated mice which carry an insertion in the gene by gene-targeting methods. Mice which are homozygous for the modification die during embryogenesis. The heterozygotes exhibit a spectrum of phenotypes including slower growth rates, lack of visual acuity in one or both eyes, and motor system abnormalities. Histochemical analysis of the severely affected mice revealed that their Purkinje cell dendritic processes are abnormal, do not react with MAP1B antibodies, and show reduced staining with MAP1A antibodies. Similar histological and immunochemical changes were observed in the olfactory bulb, hippocampus, and retina, providing a basis for the observed phenotypes.

Animals↗
PubMed1996

Inherited and acquired risk factors in colonic neoplasia and modulation by chemopreventive interventions.

The progressively abnormal development of epithelial cells prior to tumor development leads to widely differing chemopreventive approaches. The diversity of these approaches has resulted in different assays to measure the activities of the agents. To apply these assays to preclinical studies, we have developed rodent models in which different stages of evolution of colonic neoplasia are expressed. In one model mice carrying a truncated Apc allele with a nonsense mutation in exon 15 have been generated by gene targeting and embryonic stem cell technology (Apc 1638 mice). These mice develop multiple gastrointestinal lesions including adenomas and carcinomas, focal areas of high grade dysplasia (FAD) and polypoid hyperplasias with FADS. The incidence of inherited colonic neoplasms has now been modulated by a chemopreventive regimen. Colonic lesions significantly increased in Apc 1638 mice on a Western-style diet, compared to Apc 1638 mice on AIN-76A diet which has lower fat content and higher calcium and vitamin D. These studies have also been carried out in normal mice, and have demonstrated without any chemical carcinogen that a Western-style diet induced colonic tumorigenesis. Modulation of cell proliferation has also been induced by Western-style diets in other organs including mammary gland, pancreas and prostate. These findings are leading to the development of new preclinical models for evaluating the efficacy of many classes of chemopreventive agents.

Animals↗