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At least 991 records · Page 55Linked to original sources
PubMed1997

Cloning and functional expression of the luteinizing hormone receptor complementary deoxyribonucleic acid from the marmoset monkey testis: absence of sequences encoding exon 10 in other species.

Based on sequence homologies among the human, porcine, rat, and mouse genes for the LH receptor (LHR), overlapping partial fragments of LHR complementary DNAs (cDNAs) were multiplied from marmoset monkey testicular RNA using reverse transcription-PCR. Ligations of the individual cDNA fragments generated a full-length monkey LHR cDNA (2031 bp) containing the complete amino acid-coding sequence (676 amino acids). Northern hybridization analysis of monkey testicular RNA, using a complementary RNA probe corresponding to the full-length cDNA, demonstrated major transcripts of 5.5 and 1.4 kilobases and minor ones of 4.0, 2.7, and 1.9 kilobases. Sequence analysis of the monkey LHR cDNA revealed a striking feature, i.e. the absence of an 81-bp nucleotide sequence corresponding to exon 10, present in the LHR cDNAs of all other species studied to date. The monkey LHR cDNA displayed 83-94% overall sequence homology with the other mammalian LHR cDNAs. Reverse transcription-PCR with human exon 10-specific primers demonstrated the total absence of this sequence from the monkey LHR messenger RNA. Southern hybridization of monkey genomic DNA using a human exon 10 probe demonstrated its presence in the monkey gene and that it is totally spliced out from the primary transcript. COS cells transfected with the monkey LHR cDNA showed similar high affinity (Kd = 0.25 nmol/liter) of [125I]iodo-hCG binding as those transfected with human LHR cDNA (Kd = 0.20 nmol/liter). The cells expressing the recombinant monkey and human LHR displayed similar responses of extracellular cAMP and inositol trisphosphate to hCG. In conclusion, marmoset monkey LHR seems to lack the sequence corresponding to exon 10 of the LHR gene in other mammalian species. The truncation does not alter LHR function, as the monkey receptor protein bound hCG and evoked cAMP and inositol trisphosphate responses comparable to those of the human LHR containing the exon 10-encoded structure. As the sequence homologous to exon 10 is missing in the other two glycoprotein receptors, i.e. those of FSH and TSH, this extra exon is apparently inserted into the LHR messenger RNA of some species during evolution from intronic sequences by a change in alternative splicing.

Alternative Splicing↗
PubMed2004

Denaturing-HPLC-based assay for detection of ABL mutations in chronic myeloid leukemia patients resistant to Imatinib.

BACKGROUND: Despite the efficacy of the BCR-ABL tyrosine kinase inhibitor Imatinib mesylate for the treatment of chronic myeloid leukemia (CML), resistance has been observed in a proportion of cases, especially those with advanced stages of the disease. Point mutations within the ABL kinase domain are emerging as the most frequent mechanism for reactivation of kinase activity within the leukemic clone. METHODS: We developed a denaturing-HPLC (D-HPLC)-based assay for screening for ABL point mutations. For each sample, two partially overlapping fragments of 393 and 482 bp corresponding to the kinase domain were amplified by nested reverse transcription-PCR and analyzed under selected temperature and acetonitrile gradient conditions. Fifty-one bone marrow and/or peripheral blood specimens from 27 CML patients who showed cytogenetic resistance to Imatinib were screened in parallel by D-HPLC and by direct sequencing. RESULTS: In 12 of 27 (44%) patients, D-HPLC showed an abnormal elution profile suggesting the presence of a nucleotide change. Direct sequencing confirmed the presence of a point mutation in all cases. Conversely, all samples scored as wild type by D-HPLC showed no evidence of mutations by direct sequencing. In two cases, novel amino acid substitutions at codons already known for being hot-spots of mutation were identified (F311I and E355D). CONCLUSIONS: The proposed D-HPLC-based assay is highly specific and at least as sensitive as sequencing; with respect to the latter, it provides a much faster and less expensive semiautomated system for mutational screening. It may therefore potentially be a valuable tool for regular, large-scale testing of patients undergoing Imatinib treatment.

Antineoplastic Agents↗
PubMed2002

[Gene cloning and sequencing of chicken anemia virus(CAV) isolated from Harbin].

A Chicken anemia virus has been isolated from a chicken flock in Harbin of China. The genome of the ivrus was cloned through polymerase chain reaction(PCR) and sequence of the genome was analyzed. The cycle genome is made of 2298 base pairs including three overlapping open reading frames(vp1, vp2, vp3) and a regulative region. Comparing sequence of the genome through BLAST in GenBank, this sequence exhibits 96.9% identity with other genome of CA Vs and least. Multiple alignment of this genome of this virus, 26p4, strain isolated in Germany, strain isolated in Malaysia and Cux-1 found that this sequence exhibits 98.2% (42/2298), 98.2% (42/2298), 96.9% (72/2298) and 97.5% (60/2319) identify with them, respectively. A new CAV strain was isolated and it has better identify with CAV isolated in Europe countries than is Asia country Malaysia. Multiple alignment of VP1, VP2, VP3 of 26p4, strain isolated in Germany, strain isolated in Malaysia, Cux-1 and strain isolated in Harbin of China found the VP2 the most conservative.

Amino Acid Sequence↗
PubMed2000

Genotyping of factor V G1691A (Leiden) without the use of PCR by invasive cleavage of oligonucleotide probes.

BACKGROUND: The factor V G1691A Leiden (FVL) mutation is the most common known hereditary risk factor for venous thrombosis. METHODS: Third Wave Technologies, Inc. (Madison, WI) has developed a new microtiter plate-based assay that does not require PCR, restriction digestion, or gel electrophoresis. This technology system, termed the Invader(TM) assay, utilizes a 5' "invading" oligonucleotide and a partially overlapping 3' "signal" oligonucleotide, which together form a specific structure when bound to a complementary genomic DNA template. A thermostable flap endonuclease cleaves this structure, releasing the 5' flap from the signal oligonucleotide. Increased temperature and an excess of the signal probe enable multiple probes to be cleaved for each target sequence present without temperature cycling. The cleaved probes then direct cleavage of a secondary probe, which is 5' end-labeled with fluorescein but is quenched by an internal dye. Upon cleavage, the fluorescein-labeled product is detected using a standard fluorescence plate reader. Genotypes are determined by net wild-type/mutant signal ratio. RESULTS: Complete concordance was observed, after resolution of four discordances, when 1369 individuals (1264 wild type, 102 heterozygous, 3 homozygous) were FVL genotyped by both the Invader assay and by allele-specific PCR. CONCLUSION: We conclude that FVL genotyping using invasive cleavage of oligonucleotide probes is a rapid and reliable alternative to genotyping by more traditional PCR-based methods.

DNA↗
PubMed1996

Phenotypic characterization of individuals with 30-40 CAG repeats in the Huntington disease (HD) gene reveals HD cases with 36 repeats and apparently normal elderly individuals with 36-39 repeats.

Abnormal CAG expansions in the IT-15 gene are associated with Huntington disease (HD). In the diagnostic setting it is necessary to define the limits of the CAG size ranges on normal and HD-associated chromosomes. Most large analyses that defined the limits of the normal and pathological size ranges employed PCR assays, which included the CAG repeats and a CCG repeat tract that was thought to be invariant. Many of these experiments found an overlap between the normal and disease size ranges. Subsequent findings that the CCG repeats vary by 8 trinucleotide lengths suggested that the limits of the normal and disease size ranges should be reevaluated with assays that exclude the CCG polymorphism. Since patients with between 30 and 40 repeats are rare, a consortium was assembled to collect such individuals. All 178 samples were reanalyzed in Cambridge by using assays specific for the CAG repeats. We have optimized methods for reliable sizing of CAG repeats and show cases that demonstrate the dangers of using PCR assays that include both the CAG and CCG polymorphisms. Seven HD patients had 36 repeats, which confirms that this allele is associated with disease. Individuals without apparent symptoms or signs of HD were found at 36 repeats (aged 74, 78, 79, and 87 years), 37 repeats (aged 69 years), 38 repeats (aged 69 and 90 years), and 39 repeats (aged 67, 90, and 95 years). The detailed case histories of an exceptional case from this series will be presented: a 95-year-old man with 39 repeats who did not have classical features of HD. The apparently healthy survival into old age of some individuals with 36-39 repeats suggests that the HD mutation may not always be fully penetrant.

Adult↗
PubMed1993

Molecular characterization of the body site-specific human epidermal cytokeratin 9: cDNA cloning, amino acid sequence, and tissue specificity of gene expression.

Differentiation of human plantar and palmar epidermis is characterized by the suprabasal synthesis of a major special intermediate-sized filament (IF) protein, the type I (acidic) cytokeratin 9 (CK 9). Using partial amino acid (aa) sequence information obtained by direct Edman sequencing of peptides resulting from proteolytic digestion of purified CK 9, we synthesized several redundant primers by 'back-translation'. Amplification by polymerase chain reaction (PCR) of cDNAs obtained by reverse transcription of mRNAs from human foot sole epidermis, including 5'-primer extension, resulted in multiple overlapping cDNA clones, from which the complete cDNA (2353 bp) could be constructed. This cDNA encoded the CK 9 polypeptide with a calculated molecular weight of 61,987 and an isoelectric point at about pH 5.0. The aa sequence deduced from cDNA was verified in several parts by comparison with the peptide sequences and showed the typical structure of type I CKs, with a head (153 aa), and alpha-helical coiled-coil-forming rod (306 aa), and a tail (163 aa) domain. The protein displayed the highest homology to human CK 10, not only in the highly conserved rod domain but also in large parts of the head and the tail domains. On the other hand, the aa sequence revealed some remarkable differences from CK 10 and other CKs, even in the most conserved segments of the rod domain. The nuclease digestion pattern seen on Southern blot analysis of human genomic DNA indicated the existence of a unique CK 9 gene. Using CK 9-specific riboprobes for hybridization on Northern blots of RNAs from various epithelia, a mRNA of about 2.4 kb in length could be identified only in foot sole epidermis, and a weaker cross-hybridization signal was seen in RNA from bovine heel pad epidermis at about 2.0 kb. A large number of tissues and cell cultures were examined by PCR of mRNA-derived cDNAs, using CK 9-specific primers. But even with this very sensitive signal amplification, only palmar/plantar epidermis was found positive. By in situ hybridization and immunolocalization we further showed that CK 9 is only expressed in the suprabasal cell layers of this special epidermal tissue. We discuss the molecular properties of CK 9 and its cell type- and body site-specific expression in relation to the special differentiation of palmar/plantar epidermis and to diseases specific for this body site.

Amino Acid Sequence↗
PubMed1999

D1S80 subtyping by PCR-RFLP: new nomenclature and further characterization.

In a previous study, we screened out sequence variations within alleles at the D1S80 locus of a Japanese population using PCR-RFLP with EcoRII as a restriction enzyme. In the present study, through analyzing the alleles in a Chinese population, we were able to demonstrate four new electrophoretic band patterns that were complementary to the Japanese data. After summarizing the band patterns and sequencing results of these two populations, we established a new nomenclature for the PCR-RFLP band patterns, closely relating them to their corresponding sequences so that the new types could be designated easily and accurately. After PCR-RFLP subtyping, nineteen alleles in the Chinese population were revealed to have a total of thirty-seven subtypes. The discrimination power of this locus in the Chinese population was elevated from 0.974 to 0.988, and the Hardy-Weinberg equilibrium in this population showed no deviation when checked. Two samples typed as homozygotes 24/24 and 30/30 were identified to be actually heterozygous according to their band patterns. The result was supported by the sequencing analysis of the two samples in which overlapping of eight and eleven repeat units, respectively, were revealed. The heterozygosity was thus elevated from 0.85 to 0.87. The present study proved that PCR-RFLP was an effective method for subtyping D1S80 alleles in the Chinese.

Journal Article↗
PubMed2001

Structure, chromosomal localization, and expression of the gene for mouse ecto-mono(ADP-ribosyl)transferase ART5.

Mono(ADP-ribosyl)transferases regulate the function of target proteins by attaching ADP-ribose to specific amino acid residues in their target proteins. The purpose of this study was to determine the structure, chromosomal localization, and expression profile of the gene for mouse ecto-ADP-ribosyltransferase ART5. Southern blot analyses indicate that Art5 is a single copy gene which maps to mouse chromosome 7 at offset 49.6 cM in close proximity to the Art1, Art2a and Art2b genes. Northern blot and RT-PCR analyses demonstrate prominent expression of Art5 in testis, and lower levels in cardiac and skeletal muscle. Sequence analyses reveal that the Art5 gene encompasses six exons spanning 8 kb of genomic DNA. The 5' end of the Art5 gene overlaps with that of the Art1 gene. A single long exon encodes the predicted ART5 catalytic domain. Separate exons encode the N-terminal leader peptide and a hydrophilic C-terminal extension. Sequencing of RT-PCR products and ESTs identified six splice variants. The deduced amino acid sequence of ART5 shows 87% sequence identity to its orthologue from the human, and 37 and 32% identity to its murine paralogues ART1 and ART2. Unlike ART1 and ART2, ART5 lacks a glycosylphosphatidylinositol-anchor signal sequence and is predicted to be a secretory enzyme. This prediction was confirmed by transfecting an Art5 cDNA expression construct into Sf9 insect cells. The secreted epitope-tagged ART5 protein resembled rat ART2 in exhibiting potent NAD-glycohydrolase activity. This study provides important experimental tools to further elucidate the function of ART5.

ADP Ribose Transferases↗
PubMed2002

Identification of the Brucella melitensis vaccine strain Rev.1 in animals and humans in Israel by PCR analysis of the PstI site polymorphism of its omp2 gene.

Adverse effects of strain persistence and secretion in milk have been encountered with the Brucella melitensis vaccine strain Rev.1. Field isolates obtained from vaccinated animals and from a human resembled the vaccine strain Rev.1 by conventional bacteriological tests. The lack of a specific molecular marker that could specifically characterize the commercial vaccine strain prevented confirmation of the homology of the Rev.1-like field isolates to the vaccine strain. The composition of the omp2 locus from two gene copies with differences in their PstI restriction endonuclease sites was used to establish an epidemiologic fingerprint for the omp2 gene in the Rev.1 vaccine strain. Primers designed to amplify DNA sequences that overlap the PstI site revealed a single 282-bp DNA band common to all Brucella spp. Agarose gel electrophoresis of the PstI digests of the PCR products from strains 16M and the vaccine strain Rev.1 revealed a distinctive profile that included three bands: one band for the intact 282-bp fragment amplified from omp2a and two bands resulting from the digestion of the amplified omp2b gene fragment, 238- and 44-bp DNA fragments, respectively. Amplified fragments of 37 Rev.1-like isolates, including 2 human isolates, also exhibited this pattern. In contrast, DNA digests of all other Israeli field isolates, including atypical B. melitensis biotype 1 and representatives of the biotype 2 and 3 isolates, produced two bands of 238 and 44 bp, respectively, corresponding with the digestion of both omp2a and omp2b genes. This method facilitates identification of the Rev.1 vaccine strain in both animals and humans in Israel.

Abortion, Veterinary↗
PubMed1996

Mutational analysis of RAG-1 in lymphoid malignancies.

Illegitimate recombinase activity promoted by the recombination activating RAG-1 and RAG-2 is assumed to be involved in the pathogenesis of the chromosomal translocations observed in lymphoid neoplasias. We analyzed the complete coding region of the RAG-1 gene in patients with lymphoid neoplasis using a multiple PCR-SSCP (single strand conformation polymorphism) strategy. Nine multiple myelomas, 17 non-Hodgkin's lymphomas, 18 acute lymphocytic leukemias, 37 chronic lymphocytic leukemias and 33 non-neoplastic controls were studied. To screen the entire RAG-1 gene we used primers overlapping genomic segments of the RAG-1 coding sequence (nucleotides 87 to 3311). Samples with an abnormal band pattern in the SSCP were cloned and sequenced. Successful amplification was achieved with our protocol. The multiple PCR-SSCP analysis proved to be a feasible and sensitive strategy for studying variations in the sequence of the RAG-1 gene. No mutations other than the three previously reported sequence variations were detected. Although mutations in this gene do not appear to be common in lymphoid neoplasias, it would be interesting to ascertain whether the different variant forms of RAG-1 protein have an abnormal recombinase activity.

DNA Mutational Analysis↗
PubMed1991

Detection and characterization of human T-cell lymphotropic virus type I (HTLV-I) associated T-cell neoplasms in an HTLV-I nonendemic region by polymerase chain reaction.

Human T-cell lymphotropic virus type I (HTLV-I) associated adult T-cell leukemia/lymphoma (ATLL) occurs endemically in southwestern Japan, the Caribbean, and West Africa, but occurs sporadically in most of the rest of the world. However, because ATLL and non-HTLV-I associated T-cell neoplasms share overlapping clinicopathologic features, the prevalence of ATLL in nonendemic regions is unknown. In this study, 75 T-cell neoplasms randomly procured from the metropolitan New York City area were examined by polymerase chain reaction (PCR) for the presence of integrated HTLV-I proviral sequences. HTLV-I genomic sequences were detected by PCR in 6 of the 75 cases (8%); this result was confirmed by Southern blot hybridization. The clinicopathologic features of the HTLV-I positive and HTLV-I negative T-cell neoplasms were then compared. Although the clinicopathologic features of patients from these two groups overlapped, some findings were more commonly associated with HTLV-I positive neoplasms. Five of the six patients with HTLV-I positive neoplasms were from HTLV-I endemic areas, five were black, five were women, and five were less than 45 years of age, while the majority of the patients with HTLV-I negative T-cell malignancies were elderly white men. The incidence of hypercalcemia and lytic bone lesions was significantly more common among patients with HTLV-I positive T-cell neoplasms (P less than .001 and P = .004, respectively). The immunophenotypes of the HTLV-I positive and negative tumors were similar; however, all HTLV-I positive neoplasms were CD7 negative (P less than .001). In summary, our findings: (1) demonstrate the special clinicopathologic and immunophenotypic features of HTLV-I positive T-cell neoplasms, (2) suggest that most of the rare cases of HTLV-I-associated T-cell neoplasms occurring in HTLV-I nonendemic areas are actually endemic cases; and (3) that PCR is a sensitive, clinically useful technique for identifying HTLV-I associated T-cell neoplasms.

Adult↗
PubMed1996

The retrieval of ancient human DNA sequences.

DNA was extracted from approximately 600-year-old human remains found at an archaeological site in the southwestern United States, and mtDNA fragments were amplified by PCR. When these fragments were sequenced directly, multiple sequences seemed to be present. From three representative individuals, DNA fragments of different lengths were quantified and short overlapping amplification products cloned. When amplifications started from <40 molecules, clones contained several different sequences. In contrast, when they were initiated by a few thousand molecules, unambiguous and reproducible results were achieved. These results show that more experimental work than is often applied is necessary to ensure that DNA sequences amplified from ancient human remains are authentic. In particular, quantitation of the numbers of amplifiable molecules is a useful tool to determine the role of contaminating contemporary molecules and PCR errors in amplifications from ancient DNA.

Archaeology↗
PubMed2004

Rapid combined genotyping assay for four achondroplasia and hypochondroplasia mutations by real-time PCR with multiple detection probes.

Achondroplasia (ACH) and hypochondroplasia (HYCH) are the most prevalent genetic short-stature syndromes. Whereas the diagnosis of ACH can be established on clinical and radiologic grounds alone in the majority of cases, HYCH is more difficult to confirm. Molecular genetic analysis of both skeletal dysplasias can be especially helpful for the purpose of prenatal diagnosis, in early childhood to differentiate definitively between the largely overlapping phenotypes, and in atypical presentations. The two most prevalent mutations for each syndrome cause substitution of a single respective nucleotide. These mutations can be identified by a variety of molecular methods, including PCR with restriction enzyme digestion or direct DNA sequencing. We have developed a single-step, real-time PCR assay in which two detection probes are applied in combination with a single anchor probe at each mutation position. Because the two most prevalent mutations for each syndrome cause substitution of a single respective nucleotide, this approach guarantees optimal differentiation during probe dissociation analysis after amplification. This assay, which is performed on the LightCycler thermocycler, enables the rapid and reliable detection of the two most common FGFR3 mutations associated with ACH (1138G --> A and 1138G --> C; G380R) and HYCH (1620C --> A and 1620 C --> G; N540K) in a single test.

Achondroplasia↗
PubMed2006

Quantitative multiplex real-time PCR for detection of PLP1 gene duplications in Pelizaeus-Merzbacher patients.

Pelizaeus-Merzbacher disease (PMD) is an X-linked recessive disorder of central nervous system (CNS) myelination typically affecting males. A genomic duplication of variable size at Xq22.2, containing the entire proteolipid protein 1 gene (PLP1), is responsible for approximately 60-70% of PMD cases. The aim of this study was to develop a rapid and robust method for determination of PLP1 gene dosage. We optimized two multiplex real-time quantitative PCR (Q-PCR) assays targeting exons 3 and 6 of the PLP1 gene, and then validated these assays by retrospective analysis of a set of genomic DNAs from 67 previously tested patients and 43 normal controls. Samples were analyzed in multiplex PCR reactions using TaqMan chemistry and the ABI Prism 7000 Sequence Detection System. PLP1 dosage was determined by the relative quantitative comparative threshold cycle method (DeltaDeltaCt) using the human serum albumin gene as the endogenous reference gene. Three clearly non-overlapping ranges of results, corresponding to the presence of one, two, or three PLP1 copies, were detected in both assays. The results were completely concordant with gender and previous PLP1 gene dosage testing based on quantitative fluorescent multiplex PCR and analysis of a dinucleotide polymorphism in the first intron of the PLP1 gene. We conclude that multiplex real-time Q-PCR represents a fast and reliable tool for PLP1 duplication testing in PMD families.

Female↗
PubMed1995

Fundulus heteroclitus vitellogenin: the deduced primary structure of a piscine precursor to noncrystalline, liquid-phase yolk protein.

We have cloned and sequenced a cDNA encoding a vitellogenin (Vtg) from the mummichog, Fundulus heteroclitus, an estuarine teleost. We constructed a liver cDNA library against RNA from estrogen-treated male mummichogs. Five overlapping cDNA clones totalling 5,197 bp were isolated through a combination of degenerate oligonucleotide probing of the library and PCR. The cDNA sequence contains a 5,112 bp open reading frame. The predicted primary structure of the deduced 1,704-amino-acid protein is 30-40% identical to other documented chordate Vtgs, establishing this Vtg as a member of the ancient Vtg gene family. Of the previously reported chordate Vtg sequences (Xenopus laevis, Gallus domesticus, Ichthyomyzon unicuspis, and Acipenser transmontanus), all four act as precursor proteins to a yolk which is eventually rendered insoluble under physiological conditions, either as crystalline platelets or as noncrystalline granules. The yolk of F. heteroclitus, on the other hand, remains in a soluble state throughout oocyte growth. The putative F. heteroclitus Vtg contains a polyserine region with a relative serine composition that is 10-20% higher than that observed for the other Vtgs. The trinucleotide repeats encoding the characteristic polyserine tracts of the phosvitin region follow a previously reported trend: TCX codons on the 5' end and AGY codons toward the 3' end. Whether the difference in Vtg primary structure between F. heteroclitus and that of other chordates is responsible for the differences in yolk structure remains to be elucidated. As the first complete teleost Vtg to be reported, these data will aid in designing nucleotide and immunological probes for detecting Vtg as a reproductive status indicator in F. heteroclitus and other piscine species.

Amino Acid Sequence↗
PubMed2006

Cloning and expression analysis of a murine novel gene, Ayu17-449.

We used gene trapping vector PU8 to search some interesting genes which play important roles in mouse development from murine ES cells. One positive ES colony termed Ayu17-449 was trapped. Its partial cDNA was obtained by using 5' RACE method. It is homologous to a 5,523 bp cDNA fragment (GI: 20879412) in EST database. Further analysis of the 5,523 bp cDNA sequence in Celera mouse gene database showed that it overlaps two genes. We designed serials of DNA primers according to the mRNAs of these two genes for RT-PCR and Northern blotting analysis, and identified a novel RNA about 9 kb (we named it as Ayu17-449) encoding 1,920 aa. This gene is expressed highly in the brain, kidney, heart, lung, muscle and stomach. The expressed protein contains a Granin motif on its N-terminus, showing that this gene may be involved in hormone secretion.

Animals↗
PubMed1999

Expression of the alpha 6A integrin splice variant in developing mouse embryonic stem cell aggregates and correlation with cardiac muscle differentiation.

Mouse embryonic stem (ES) cells grown in aggregates give rise to several different cell types, including cardiac muscle. Given the lack of cardiac muscle cell lines, ES cells can be a useful tool in the study of cardiac muscle differentiation. The laminin-binding integrin alpha 6 beta 1 exists in two different splice variant forms of the alpha chain (alpha 6A and alpha 6B), the alpha 6A form having been implicated as possibly playing a role in cardiac muscle development, based on its distribution pattern [4, 53]. In this study we characterise the ES cell model system in terms of the expression of the two different alpha 6 splice variants. We correlate their expression with that of muscle markers and the transcription factor GATA-4, using the reverse transcription-polymerase chain reaction (RT-PCR). We confirm that alpha 6B is constitutively expressed by ES cells. In contrast, alpha 6A expression appears later and overlaps in time with a period when the muscle marker myosin light chain-2V (MLC-2V) is expressed, but no MyoD is present, which indicates the presence of cardiac muscle cells in the aggregates. We further show that GATA-4 is present at the same time. Culturing the aggregates under conditions that stimulate (transforming growth factor beta 1 supplement) or inhibit (TGF beta 1 plus 10(-9) M retinoic acid supplement) cardiac muscle differentiation does not lead to any qualitative differences in the timing of expression of these genes, but quantitative changes cannot be excluded. The TGF beta 1 supplement does, however, lead to a relatively greater expression of alpha 6A compared to alpha 6B than the TGF beta 1 plus 10(-9) M RA supplement after 6 days in culture, suggesting that alpha 6A expression is favoured under conditions that stimulate cardiac muscle differentiation. The switch towards alpha 6A expression in ES cell aggregates is paralleled by expression of the binding receptor for TGF beta (T beta RII). Stable expression of a mutated (dominant negative) T beta RII in ES cells, however, still resulted in (TGF beta-independent) upregulation of alpha 6A, demonstrating that these events were not causally related and that parallel or alternative regulatory pathways exist. The initial characterisation of differentiating ES cell aggregates in terms of alpha 6A integrin subunit expression suggests that this model system could be a valuable tool in the study of the role of the alpha 6A beta 1 integrin in cardiac muscle differentiation.

Animals↗
PubMed1991

Structure of the human hexabrachion (tenascin) gene.

The structure of the gene encoding human hexabrachion (tenascin) has been determined from overlapping clones isolated from a human genomic bacteriophage library. The genomic inserts were characterized by restriction mapping, Southern blot analysis, PCR, and DNA sequencing. The coding region of the hexabrachion gene spans approximately 80 kilobases of DNA and consists of 27 exons separated by 26 introns. The exon-intron structure supports a hypothesis based on the cDNA sequence that the hexabrachion gene is an assembly of DNA modules that are also found elsewhere in the genome. Single exons may encode a module, a portion of a module, or a group of modules. The 15 type III units similar to those found in fibronectin are each encoded either by a single exon or by two exons interrupted by an intron. All type III units known to be spliced out of the smaller forms of the protein are encoded by one exon. The fibrinogen-like domain of 210 amino acids is encoded by five exons. The 14.5 epidermal growth factor-like repeats are all encoded by a single exon.

Amino Acid Sequence↗