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Biomedical subjects

T L Yang-Feng

Publications and source records attributed to T L Yang-Feng.

At least 73 records · Page 4Linked to original sources
PubMed1992

Unusual distribution of Zfy and Zfx sequences on the sex chromosomes of the wood lemming, a species exhibiting XY sex reversal.

Sex reversal occurs naturally in the wood lemming (Myopus schisticolor) due to the presence in populations of this species of a variant (mutated) X chromosome, designated X*. Thus, X*Y animals develop into females, whereas XY animals develop into normal males. Chromosome mapping by in situ hybridization of DNA sequences homologous to the human ZFY gene localized the wood lemming Zfx sequences to region p12----p11 on both the wild-type X and the mutated X* chromosomes, at or proximal to a presumed breakpoint (Xp12) involved in the generation of the X* chromosome from the normal X, and Zfy sequences along the entire short arm of the Y chromosome. Differences between Zfx and Zfx* were readily detected by Southern blot analysis. However, both the Zfx and Zfx* genes expressed similarly sized transcripts in all adult somatic tissues investigated. Although the precise molecular difference between the Zfx and Zfx* genes is still unknown, their chromosomal location suggests that either Zfx or some other closely linked gene(s) on the X chromosome may be a major X-linked sex-determining gene, Tdx, which in the X* chromosome fails to interact properly with the Y-linked testis-determining gene, Tdy, thus causing X*Y embryos to develop into females. At least 15 copies of wood lemming Zfy sequences are distributed along the short arm of the Y chromosome. Northern hybridization analyses of adult tissues and somatic cell lines indicated that these Zfy repeats were transcriptionally inactive. Normally, 3-kb Zfy (ZFY) transcripts are readily detected in mouse and human testes, especially in the germ cells. It has therefore been postulated that expression of the Zfy (ZFY) gene may be important for spermatogenesis. Whether the lack of sufficient Zfy transcripts in the testis of the adult wood lemming has any impact on spermatogenesis in this species is still to be elucidated by further studies.

Animals↗
PubMed1992

Phenotypic, cytogenetic, and molecular studies of three patients with constitutional deletions of chromosome 5 in the region of the gene for familial adenomatous polyposis.

We have studied three patients, one with extensive polyposis of the colon, who have constitutional interstitial deletions of the long arm of chromosome 5. High-resolution banding studies indicated that the deletion in the patient with polyposis spans the region 5q21-q22, which includes APC, a gene involved in familial adenomatous polyposis and sporadic colon cancer. Molecular analysis with probes for sequences flanking APC confirmed this conclusion. The deletions in the other two patients, who are too young to have developed polyposis, had breakpoints within this region, precluding the use of cytogenetic analysis alone in making definitive predictions about their risks. Molecular studies resolved the uncertainty; in situ and quantitative Southern hybridizations of four probes for polymorphic segments revealed that one of the patients has a deletion of MCC, a gene which is approximately 150 kb proximal to APC, and two flanking markers. He is at increased risk for polyposis, while the other patient is not. The physical descriptions of these patients, in conjunction with cases in the literature, begin to allow delineation of two distinct 5q-syndromes. These studies also provide precise physical mapping data for D5S71, D5S81, D5S84, and MCC on 5q.

Abnormalities, Multiple↗
PubMed1992

Molecular definition of the smallest region of deletion overlap in the Wolf-Hirschhorn syndrome.

Wolf-Hirschhorn syndrome (WHS), associated with a deletion of chromosome 4p, is characterized by mental and growth retardation and typical facial dysmorphism. A girl with clinical features of WHS was found to carry a subtle deletion of chromosome 4p. Initially suggested by high-resolution chromosome analysis, her deletion was confirmed by fluorescence in situ hybridization (FISH) with cosmid probes, E13 and Y2, of D4S113. To delineate this 4p deletion, we performed a series of FISH and pulsed-field gel electrophoresis analyses by using probes from 4p16.3. A deletion of approximately 2.5 Mb with the breakpoint at approximately 80 kb distal to D4S43 was defined in this patient and appears to be the smallest WHS deletion so far identified. To further refine the WHS critical region, we have studied three unrelated patients with presumptive 4p deletions, two resulting from unbalanced segregations of parental chromosomal translocations and one resulting from an apparently de novo unbalanced translocation. Larger deletions were identified in two patients with WHS. One patient who did not clinically present with WHS had a smaller deletion that thus eliminates the distal 100-300 kb from the telomere as being part of the WHS region. This study has localized the WHS region to approximately 2 Mb between D4S43 and D4S142.

Abnormalities, Multiple↗
PubMed1991

Cloning, molecular characterization, and chromosomal assignment of a gene encoding a second D1 dopamine receptor subtype: differential expression pattern in rat brain compared with the D1A receptor.

Multiple D1 dopaminergic receptor subtypes have been postulated on the basis of pharmacological, biochemical, and genetic studies. We describe the isolation and characterization of a rat gene encoding a dopamine receptor that is structurally and functionally similar to the D1 dopamine receptor. The coding region, which is intronless, encodes a protein of 475 amino acids (Mr 52,834) with structural features that are consistent with receptors coupled to guanine nucleotide-binding regulatory proteins. The expressed protein binds dopaminergic ligands and mediates stimulation of adenylyl cyclase with pharmacological properties similar to those of the D1 dopamine receptor. The gene encoding the human homologue of this receptor subtype is located to the short arm of chromosome 4 (4p16.3), the same region as the Huntington disease gene. In striking contrast to the previously cloned D1 receptor, little or no mRNA for the receptor described here was observed in striatum, nucleus accumbens, olfactory tubercle, and frontal cortex. High levels of mRNA for this receptor were found in distinct layers of the hippocampus, the mammillary nuclei, and the anterior pretectal nuclei, brain regions that have been shown to exhibit little or no D1 dopamine receptor binding. On the basis of its properties we propose that this dopamine receptor subtype be called D1B.

Amino Acid Sequence↗
PubMed1991

Trisomy 12 and K-ras-2 amplification in human ovarian tumors.

Cytogenetic analysis was performed on 11 benign and borderline ovarian tumors. Trisomy 12, identified as a sole abnormality in 6 tumors, is likely a specific karyotypic change in different benign and borderline tumors and may well be a primary chromosomal lesion in these tumors. The possible association between amplification of the proto-oncogene K-ras-2 which is located on chromosome 12 and trisomy 12 was investigated. DNA blotting analysis of 64 tumors indicates that trisomy 12 does not seem to be related to K-ras-2 amplification in ovarian tumors. K-ras-2 amplification was observed in 3 high-grade tumors from 3 patients with metastases.

Chromosome Banding↗
PubMed1991

der(3)t(3;5). Another recurring abnormality in myelodysplastic disorder.

Monosomy for chromosome 5 or a portion of the long arm is a common finding in acute nonlymphocytic leukemia (ANLL) and myelodysplastic syndrome (MDS), especially when the disorder is therapy related [1,2]. If only a portion of chromosome 5 is missing, the loss is usually accomplished by interstitial deletion of various bands, most frequently q12-14 to q31-33 [3]. Occasionally monosomy for 5q is the result of a translocation between chromosome 5 and another chromosome, with the loss of the derivative chromosome that contains 5q. A previously described unbalanced translocation involves chromosome 7: [der(5)t(5;7)(q11.2;p11.2)] and appears to be a recurring abnormality in these disorders [4]. We report here one case of therapy related MDS, one case of MDS which may be therapy related, and two cases of MDS with another "variant" 5q - abnormality, namely a derivative chromosome 3 composed of most of the short arm of chromosome 5 and the long arm of chromosome 3: [der(3)t(3;5)(?p11;?p11)].

Aged↗
PubMed1991

Allele loss at the retinoblastoma locus in human ovarian cancer.

To gain a broad spectrum on allelic loss of specific loci in ovarian tumors, we initially examined DNA from 23 pairs of ovarian tumors and matched peripheral blood lymphocyte samples from the same patients, using 27 polymorphic DNA markers distributed on 13 chromosomes. Significant high frequency of allelic deletion (22%-44%) at chromosome 13 loci (D13S31, D13S32, D13S33, and D13S34) at bands q12-q34 was observed in tumor tissues. These results led us to investigate the loss of heterozygosity at the retinoblastoma (RB) locus in ovarian tumors, because the RB gene is a tumor-suppressor gene located at 13q14. Analysis of the variable number of tandem repeat sequence polymorphism in intron 20 in the RB gene revealed that 6 (30%) of 20 patients with informative samples showed allelic loss at the RB locus in their tumor tissues. This loss, of relatively high frequency, suggests that the RB gene, or a closely linked gene, seems to be involved in the development of ovarian cancer.

Base Sequence↗
PubMed1991

Molecular cloning and expression of the cDNA for the alpha 1A-adrenergic receptor. The gene for which is located on human chromosome 5.

Pharmacological and molecular cloning studies have demonstrated heterogeneity of alpha 1-adrenergic receptors. We have now cloned two alpha 1-adrenergic receptors from a rat cerebral cortex cDNA library, using the hamster alpha 1B-adrenergic receptor as a probe. The deduced amino acid sequence of clone RA42 encodes a protein of 560 amino acids whose putative topology is similar to that of the family of G-protein-coupled receptors. The primary structure though most closely resembles that of an alpha 1-adrenergic receptor, having approximately 73% amino acid identity in the putative transmembrane domains with the previously isolated hamster alpha 1B receptor. Analysis of the ligand binding properties of RA42 expressed in COS-7 cells with a variety of adrenergic ligands demonstrates a unique alpha 1-adrenergic receptor pharmacology. High affinity for the antagonist WB4101 and agonists phenylephrine and methoxamine suggests that cDNA RA42 encodes the alpha 1A receptor subtype. Northern blot analysis of various rat tissues also shows the distribution expected of the alpha 1A receptor subtype with abundant expression in vas deferens followed by hippocampus, cerebral cortex, aorta, brainstem, heart and spleen. The second alpha 1-adrenergic receptor cloned represents the rat homolog of the hamster alpha 1B subtype. Expression of mRNA for this receptor is strongly detected in liver followed by heart, cerebral cortex, brain stem, kidney, lung, and spleen. This study provides definitive evidence for the existence of three alpha 1-adrenergic receptor subtypes.

Amino Acid Sequence↗
PubMed1991

"Pseudomosaicism" for 4p- in amniotic fluid cell culture proven to be true mosaicism after birth.

Pseudomosaicism is noted in approximately 1% of amniotic fluid cell studies. Some represent numerical abnormalities, but pseudomosaicism for structural chromosomal abnormalities is also seen. Pseudomosaicism is not usually considered clinically significant. Recently, we evaluated a 13-month-old girl with developmental delay and minor anomalies suggestive of 4p- syndrome. In 5 of 100 peripheral lymphocytes, she had a deletion 46,XX,del(4)(p15). Review of a prenatal amniocentesis study performed on the mother of our patient disclosed that one colony of 18 examined from 2 in situ cultures had the same abnormality, whereas none of the 27 cells from a flask culture showed the abnormality. Results of this study had originally been reported as showing pseudomosaicism. To our knowledge, amniotic fluid pseudomosaicism of a structural abnormality has not previously been shown to reflect true mosaicism in fetal tissue or liveborn children. The actual incidence of this phenomenon is unknown, but it may be present in unexamined children with minimal clinical findings. Apparently only one previous case of mosaic 4p- in a liveborn individual has been reported.

Amniocentesis↗
PubMed1991

Human interleukin-9: genomic sequence, chromosomal location, and sequences essential for its expression in human T-cell leukemia virus (HTLV)-I-transformed human T cells.

We have isolated the genomic sequence of human interleukin-9 (IL-9) based on its sequence homology with a human IL-9 cDNA isolated from human T-cell leukemia virus (HTLV)-I-transformed T cells by expression cloning. The entire genomic sequence has been determined and the gene consists of five exons and four introns. The human IL-9 gene is mapped to the long arm of human chromosome 5 at band 5q31-32, a region found to be deleted in a number of patients with acquired 5q- abnormalities and hematologic disorders. Several blocks of transcriptional control sequences have been identified at the 5'-flanking region of the human IL-9 gene that may play an important role in the control of IL-9 gene expression. The 5'-regulatory region of the human IL-9 gene also contains sequences identified in the 5'-flanking regions of other cytokine genes mapped to the long arm of human chromosome 5, including IL-3, IL-4, IL-5, and granulocyte-macrophage colony-stimulating factor and other T-cell growth factor genes including IL-2 and IL-6. The IL-9 gene is constitutively expressed in the HTLV-I-transformed human T cells and the expression of IL-9 in these cells can be further induced by 12-O-tetradecanoyl phorbol 13-acetate. Transient transfection analysis using the plasmid containing the 5'-flanking region of IL-9 gene upstream from the firefly luciferase ciferase report gene indicated that the 0.9-kb Smal-Sacl fragment of the IL-9 gene contains sequences required for the constitutive and activated expression of IL-9 gene in HTLV-I-transformed cells. These results will now allow us to study the regulatory mechanism of IL-9 gene expression in normal and leukemic human T cells.

Amino Acid Sequence↗
PubMed1991

Isolation and chromosomal localization of a novel nonerythroid ankyrin gene.

Immunoreactive isoforms of erythrocyte ankyrin have been shown to be present in a variety of nonerythroid tissues. Isolation of the genes that encode these isoforms will clarify their relationship to erythrocyte ankyrin. Using an erythrocyte ankyrin cDNA clone as a hybridization probe, we screened a human genomic library and isolated a clone that hybridizes with the probe at low stringency but not at high stringency. Partial nucleotide sequence of the clone revealed the presence of a 99-bp segment that is homologous to an exon of the erythrocyte ankyrin gene. Northern analysis showed that a labeled fragment of the clone hybridized to a 7-kb message in RNA of fetal brain but not of erythroid cells, suggesting that this clone is part of a novel gene that is expressed predominantly in nonerythroid tissue. Comparison of the sequence of the genomic clone with that of a recently isolated cDNA clone for brain ankyrin (Otto et al., 1989) showed identity of 96 of 99 bp between the putative exon and a segment of the cDNA clone (V. Bennett, personal communication, 1991), suggesting that the genomic clone is part of a gene for nonerythroid ankyrin, which we have designated ANK2. By analysis of somatic cell hybrids and fluorescence in situ hybridization, we assigned ANK2 to human chromosome 4 at a position equivalent to bands 4q25-q27.

Amino Acid Sequence↗
PubMed1991

Mapping of the human casein kinase II catalytic subunit genes: two loci carrying the homologous sequences for the alpha subunit.

The human serine/threonine protein casein kinase II (CK II) contains two distinct catalytic subunits, alpha and alpha 1, which are encoded by different genes. A combination of segregation analysis of rodent-human hybrid cells and chromosomal in situ hybridization have localized the human CK II-alpha DNA sequence to two loci: 11p15.5-p15.4 and 20p13. In contrast, the CK II-alpha' gene has been mapped to chromosome 16 by somatic cell hybrid analysis. Taken together with our previous assignment of the CK II regulatory beta-subunit gene to 6p12-p21, these results indicate that although the products of these genes form a single biological complex, they are encoded on different human chromosomes. Further analysis should determine whether both loci of CK II-alpha are functional, or perhaps one of the two constitutes a pseudogene.

Blotting, Southern↗
PubMed1991

Sequence and localization of a partial cDNA encoding the human alpha 3 chain of type IV collagen.

A novel type IV collagen, alpha 3(IV), has recently been identified in human and bovine basement membranes. Here we describe the cloning and sequencing of a cDNA encoding 218 residues of the NC1 domain of the human alpha 3(IV) chain. Of interest is the possible role of abnormalities of the alpha 3(IV) chain in Alport syndrome, as suggested by the failure to detect the NC1 domain of alpha 3(IV) in the basement membranes of some Alport syndrome patients. To determine whether the alpha 3(IV) gene (COL4A3) may be mutated in Alport syndrome, we localized it, by somatic cell hybrid analysis and in situ hybridization of metaphase chromosomes, to chromosome 2q35-2q37. Mutations in alpha 3(IV) cannot therefore be responsible for the vast majority of cases of Alport syndrome, which have been shown to be X linked. One explanation for the immunochemical data implicating alpha 3(IV) in Alport syndrome pathogenesis is that mutations of the alpha 5(IV) chain, which has been localized to Xq22 and found to be mutated in at least three kindreds with Alport syndrome, lead to failure to incorporate the alpha 3(IV) chains into the multimeric structure of glomerular basement membrane in a stable fashion.

Amino Acid Sequence↗
PubMed1990

Molecular cloning and expression of the cDNA for a novel alpha 1-adrenergic receptor subtype.

A novel alpha 1-adrenergic receptor subtype has been cloned from a bovine brain cDNA library. The deduced amino acid sequence is that of a 466-residue polypeptide. The structure is similar to that of the other adrenergic receptors as well as the larger family of G protein-coupled receptors that have a presumed seven-membrane-spanning domain topography. The greatest sequence identity of this receptor protein is with the previously cloned hamster alpha 1B-adrenergic receptor being approximately 72% within the presumed membrane-spanning domains. Localization on different human chromosomes provides evidence that the bovine cDNA is distinct from the hamster alpha 1B-adrenergic receptor. The bovine cDNA clone expressed in COS7 cells revealed 10-fold higher affinity for the alpha 1-adrenergic antagonists WB4101 and phentolamine and the agonist oxymetazoline as compared with the alpha 1B receptor, results similar to pharmacologic binding properties described for the alpha 1A receptor. Despite these similarities in pharmacological profiles, the bovine alpha 1-adrenergic receptor is sensitive to inhibition by the alkylating agent chloroethylclonidine unlike the alpha 1A-adrenergic receptor subtype. In addition, a lack of expression in tissues where the alpha 1A subtype exists suggests that this receptor may actually represent a novel alpha 1-adrenergic receptor subtype not previously appreciated by pharmacological criteria.

Adrenergic alpha-Agonists↗
PubMed1990

Duplication of euchromatin without phenotypic effects: a variant of chromosome 16.

A family with an unusual variant of chromosome 16 is presented. The mother and son both with additional material present in the short arm of chromosome 16 adjacent to the centromere are phenotypically normal. The extra C-band negative region has been shown not to be composed of alpha satellite DNA. The literature regarding other familial cases of what appears to be the same variant of chromosome 16 is reviewed.

Adult↗
PubMed1990

Novel isodicentric chromosome 18 in an abnormal infant with a mosaic karyotype [46,XY/46,XY,-18,+dic(18)(q12.2]).

A previously unreported isodicentric chromosome 18 was discovered in an abnormal infant boy whose mosaic karyotype was 46,XY/46,XY,-18,+idic(18)(q12.2). His constellation of congenital anomalies was typical of the 18q-syndrome. The clinical and cytogenetic characteristics of this patient are reported, and the literature concerning isochromosomes of 18 is reviewed.

Chromosome Aberrations↗