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M Buckingham

Publications and source records attributed to M Buckingham.

At least 73 records · Page 4Linked to original sources
PubMed1991

The apical ectodermal ridge regulates Hox-7 and Hox-8 gene expression in developing chick limb buds.

We show that expression of the two related chicken homeo box genes, Hox-7 and Hox-8, which is widespread in the lateral mesoderm at early stages, becomes restricted to the mesoderm underlying the apical ectodermal ridge as limbs develop. Expression in the limb bud mesoderm is not maintained in the limbless mutant, which does not form an apical ridge. The mutant can be rescued by grafting normal ectoderm to the limb field. This leads to expression of the two homeo box genes in the mesoderm under the induced ridge. Phenocopies of eudiplopodia, which form an ectopic ridge on the limb bud, express the two genes under both ridges. When a quail ridge is grafted over nonexpressing mesoderm, a new site of expression is induced. Therefore, Hox-7 and Hox-8 depend on a functional ridge for their continued expression in the limb bud and can be induced by it.

Amino Acid Sequence↗
PubMed1991

Early expression of the myogenic regulatory gene, myf-5, in precursor cells of skeletal muscle in the mouse embryo.

We have analysed by in situ hybridization the expression of myf-5, the murine homologue of the human myogenic regulatory sequence myf5, during embryogenesis in the mouse. myf-5 sequences were first detected in the earliest somites (from about 8 days p.c.) in the dermomyotome, before formation of the dermatome, myotome and sclerotome. The dermomyotome is classically considered to give rise to the precursor muscle cells of body and limb skeletal muscle. myf-5-positive cells were also detected early in the visceral arches and limb buds. In this case, as in somites, myf-5 expression precedes that of the two related myogenic regulatory sequences, myogenin and MyoD1, and indeed any other skeletal muscle marker examined to date. myf-5 is not detected at any stage in developing cardiac muscle. From 11.5 days p.c., the level of myf-5 transcripts begins to decrease to become undetectable (by in situ hybridization) from 14 days p.c. Both the appearance and disappearance of myf-5 follow the anteroposterior gradient of somite formation and maturation in the embryo. The time and place of myf-5 expression are consistent with a role in the early events of myogenic differentiation, possibly during determination of the myogenic lineage.

Animals↗
PubMed1990

Genetic analysis of the interaction between cardiac and skeletal actin gene expression in striated muscle of the mouse.

The two sarcomeric actin genes, encoding alpha-cardiac and alpha-skeletal actins, are co-expressed in striated muscle, but in the adult the respective isoform predominates in cardiac or skeletal muscle of the normal mouse. We have investigated the interaction between this gene pair in different genetic contexts. Northern blot analysis of alpha-actin mRNA levels in different inbred mice (129/SJ, C3H, C57BL/6) demonstrates variation of as much as threefold in skeletal muscle and eightfold in cardiac muscle. High or low-level expression is seen for both skeletal and cardiac muscle in a given line, suggesting common regulatory phenomena affecting the abundant alpha-skeletal or alpha-cardiac transcript. In the BALB/c mouse, which has a mutant cardiac actin locus, skeletal as well as cardiac actin mRNA and protein accumulate in the adult heart. We have analysed the role of the two alpha-actin genes in this phenomenon in seven recombinant inbred mouse lines (BALB/c x C57BL/6) and in a cross (BALB/c x C3H). The results demonstrate that neither alpha-actin gene alone is sufficient, and implicate other regulatory loci. DNA sequencing of the C3H and BALB/c alpha-skeletal actin gene promoters shows that they are virtually identical over 830 nucleotides. The relative levels of alpha-skeletal and alpha-cardiac actin proteins have been measured by N-terminal peptide analysis in the different mouse lines. The results point to regulatory loci affecting mRNA utilization and protein stability.

Actins↗
PubMed1990

The human homeobox gene HOX7 maps to chromosome 4p16.1 and may be implicated in Wolf-Hirschhorn syndrome.

A cosmid containing the human sequence (HOX7) homologous to the mouse homeogene Hox-7 was isolated from a genomic cosmid library. There is only one highly conserved homologous gene in the human genome. The C-terminal two-thirds of the HOX7 homeobox DNA sequence has been determined; there are no predicted amino acid changes from the mouse sequence. Data from mouse/human hybrid cell lines show that HOX7 maps to human chromosome 4p16.1, a region that is syntenic with part of mouse chromosome 5, the site of the murine Hox-7 gene. Analysis of chromosomes from two patients with Wolf-Hirschhorn syndrome, which is characterised by profound dysmorphologies, indicates that the HOX7 locus is deleted. Although not all Wolf-Hirschhorn syndrome patients analysed were deleted for HOX7, the combination of positional data and functional correlation with mouse expression implicates HOX7 as a candidate gene for this syndrome.

Animals↗
PubMed1990

The expression of myosin genes in developing skeletal muscle in the mouse embryo.

Using in situ hybridization, we have investigated the temporal sequence of myosin gene expression in the developing skeletal muscle masses of mouse embryos. The probes used were isoform-specific, 35S-labeled antisense cRNAs to the known sarcomeric myosin heavy chain and myosin alkali light chain gene transcripts. Results showed that both cardiac and skeletal myosin heavy chain and myosin light chain mRNAs were first detected between 9 and 10 d post coitum (p.c.) in the myotomes of the most rostral somites. Myosin transcripts appeared in more caudal somites at later stages in a developmental gradient. The earliest myosin heavy chain transcripts detected code for the embryonic skeletal (MHCemb) and beta-cardiac (MHC beta) isoforms. Perinatal myosin heavy chain (MHCpn) transcripts begin to accumulate at 10.5 d p.c., which is much earlier than previously reported. At this stage, MHCemb is the major MHC transcript. By 12.5 d p.c., MHCpn and MHCemb mRNAs are present to an equal extent, and by 15.5 d p.c. the MHCpn transcript is the major MHC mRNA detected. Cardiac MHC beta transcripts are always present as a minor component. In contrast, the cardiac MLC1A mRNA is initially more abundant than that encoding the skeletal MLC1F isoform. By 12.5 d p.c. the two MLC mRNAs are present at similar levels, and by 15.5 d p.c., MLC1F is the predominant MLC transcript detected. Transcripts for the ventricular/slow (MLC1V) and another fast skeletal myosin light chain (MLC3F) are not detected in skeletal muscle before 15 d p.c., which marks the beginning of the fetal stage of muscle development. This is the first stage at which we can detect differences in expression of myosin genes between developing muscle fibers. We conclude that, during the development of the myotome and body wall muscles, different myosin genes follow independent patterns of activation and accumulation. The data presented are the first detailed study of myosin gene expression at these early stages of skeletal muscle development.

Animals↗
PubMed1990

Developmental regulation of myosin gene expression in mouse cardiac muscle.

Expression of the two isoforms of cardiac myosin heavy chain (MHC), MHC alpha and MHC beta, in mammals is regulated postnatally by a variety of stimuli, including serum hormone levels. Less is known about the factors that regulate myosin gene expression in rapidly growing cardiac muscle in embryos. Using isoform-specific 35S-labeled cRNA probes corresponding to the two MHC genes and the two myosin alkali light chain (MLC) genes expressed in cardiac muscle, we have investigated the temporal and spatial pattern of expression of these different genes in the developing mouse heart by in situ hybridization. Between 7.5 and 8 d post coitum (p.c.), the newly formed cardiac tube begins to express MHC alpha, MHC beta, MLC1 atrial (MLC1A), and MLC1 ventricular (MLC1V) gene transcripts at high levels throughout the myocardium. As a distinct ventricular chamber forms between 8 and 9 d p.c., MHC beta mRNAs begin to be restricted to ventricular myocytes. This process is complete by 10.5 d p.c. During this time, MHC alpha mRNA levels decrease in ventricular muscle cells but continue to be expressed at high levels in atrial muscle cells. MHC alpha transcripts continue to decrease in ventricular myocytes until 16 d p.c., when they are detectable at low levels, but then increase, and finally replace MHC beta mRNAs in ventricular muscle by 7 d after birth. Like MHC beta, MLC1V transcripts become restricted to ventricular myocytes, but at a slower rate. MLC1V mRNAs continue to be detected at low levels in atrial cells until 15.5 d p.c. MLC1A mRNA levels gradually decrease but are still detectable in ventricular cells until a few days after birth. This dynamic pattern of changes in the myosin phenotype in the prenatal mouse heart suggests that there are different regulatory mechanisms for cell-specific expression of myosin isoforms during cardiac development.

Aging↗
PubMed1989

Expression of two myogenic regulatory factors myogenin and MyoD1 during mouse embryogenesis.

MyoD1 and myogenin are muscle-specific proteins which can convert non-myogenic cells in culture to differentiated muscle fibres, implicating them in myogenic determination. The pattern of expression of MyoD1 and myogenin during the early stages of muscle formation in the mouse embryo in vivo and in limb-bud explants cultured in vitro, indicates that they may have different functions in different types of muscle during development.

Animals↗
PubMed1989

Hox-7, a mouse homeobox gene with a novel pattern of expression during embryogenesis.

A new mouse Hox locus, Hox-7, is defined on chromosome 5 by a gene homologous to the Drosophila gene msh, which contains a homeobox sequence distantly related to that of Antennapedia. By in situ hybridization, expression of Hox-7 is detected in the neural fold of embryos, and also in cephalic neural crest. In addition, expression takes place in the developing valves of the embryonic heart. Mandibular and hyoid arches are strongly labelled, expression becoming restricted to the most distal part of mouth and face processes as development proceeds. Intense labelling is also observed in developing limb buds, in the distal region which has been shown to be essential for limb morphogenesis. The pronounced accumulation and regional localization of Hox-7 transcripts in mandibular and limb processes point to a specific morphogenetic role for this mouse homeobox gene.

Amino Acid Sequence↗
PubMed1989

Chromosomal assignment of two myosin alkali light-chain genes encoding the ventricular/slow skeletal muscle isoform and the atrial/fetal muscle isoform (MYL3, MYL4).

In all eukaryotes, myosin plays a major role in the maintenance of cell shape and in cellular movement; in association with actin and other contractile proteins it is also a major structural component of the muscle sarcomere. Several isoforms of myosin alkali light chain have been identified, associated with different muscle types. We have recently localized the gene encoding the fast skeletal muscle alkali light-chain isoforms MLC1F and MLC3F (HGM symbol, MYL1) to human chromosome 2q32.1-qter (Cohen-Haguenauer 1988). We present here the chromosomal assignment of two loci encoding the ventricular muscle isoform MLC1V (equivalent to the slow skeletal muscle isoform MLC1Sb) and the atrial muscle isoform MLC1A (equivalent to the fetal isoform MLC1emb) using a panel of 25 independent man-rodent somatic cell hybrids. The MLC1V gene (HGM symbol, MYL3) was mapped to human chromosome 3 using a human full-length cDNA probe that hybridizes to a single major human TaqI2.8-kb fragment. The MLC1A probe (HGM symbol, MYL4) was a 360-bp mouse cDNA fragment that gave a distinct signal with human DNA using low stringency conditions of hybridization and washings and after presaturation of the Southern blots with rodent DNA. A single PstI 7.8-kb fragment gives an intense signal, and its presence correlates with the presence of chromosome 17 among the hybrids. These data are in keeping with the localizations of the MLC1V gene to mouse chromosome 9, and of the MLC1A gene to mouse chromosome 11, which share some markers in common with human chromosomes 3 and 17 respectively.

Animals↗
PubMed1989

Nonsynchronous accumulation of alpha-skeletal actin and beta-myosin heavy chain mRNAs during early stages of pressure-overload--induced cardiac hypertrophy demonstrated by in situ hybridization.

The development of cardiac hypertrophy secondary to pressure overload is accompanied by isoformic changes of contractile proteins such as myosin and actin. 35S-Labeled complementary RNA (cRNA) probes and in situ hybridization procedures were used for analysis of the regional distribution of newly formed transcripts from alpha-skeletal actin (alpha-sk-actin) and beta-myosin heavy chain (beta-MHC) genes during the early stages of pressure overload. The study was performed in 25-day-old rats submitted to a thoracic aortic stenosis and killed after surgery at times ranging from 4 hours to 3 days. Neither alpha-sk-actin nor beta-MHC messenger RNA (mRNA) was detected in the hearts of normal and sham-operated animals. However, alpha-sk-actin mRNA accumulated throughout the entire left ventricle as early as 4 hours after aortic stenosis, and by 12 hours was also detected in the left atrium. In contrast, beta-MHC mRNA was hardly detectable before day 1, and by days 2-3 was mainly restricted to the inner part of the left ventricle and around the coronary arteries. The absence of spatial and temporal coordination in the accumulation of alpha-sk-actin and beta-MHC mRNAs indicates that different signals and/or regulatory mechanisms are implicated in the induction of the two genes in response to hemodynamic overload.

Actins↗
PubMed1989

Selective OKT3 induction therapy in adult cadaveric-donor renal transplant recipients.

Decreasing Medicare reimbursement for renal transplantation has placed a premium on early hospital discharge. On average, the diagnosis-related group reimbursement for renal transplantation is exhausted by the ninth hospital day at the authors' institution. Previously, the median length of hospital stay was 14 days for patients with initial graft dysfunction and 8 days for those with immediate function. In the present protocol, all patients received a single 10-mg dose of OKT3 during the transplant procedure. Those with good initial function received no further OKT3 and began receiving cyclosporine, 10 mg/kg/d, on the second posttransplant day. High-dose cyclosporine was avoided in those with poor initial function, whether they required dialysis or not. Instead, they received cyclosporine, 6 mg/kg/d and resumed OKT3, 5 mg/d, on the second day for up to a 14-day course to prevent rejection during recovery of renal function and permit early discharge. All patients received maintenance immunosuppression including cyclosporine, azathioprine, and prednisone. Of 39 adult cadaveric-donor renal transplant recipients entered in the protocol with 2 to 8 months follow-up, 13 (33%) had good graft function and received only the intraoperative dose of OKT3, 9 (23%) had poor initial function but did not require dialysis, and 17 (44%) had poor function receiving dialysis for a median duration of 15 days (range, 2-46 days). Side effects of OKT3 were well tolerated, and median hospital stays were 7 days (range, 6-11), 7 days (range, 5-14), and 9 days (range, 5-15), respectively, for the three groups. Overall patient survival was 100% and graft survival was 97% for the short follow-up period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Functional activity of the two promoters of the myosin alkali light chain gene in primary muscle cell cultures: comparison with other muscle gene promoters and other culture systems.

Proximal upstream flanking sequences of the mouse myosin alkali light chain gene encoding MLC1F and MLC3F, the mouse alpha-cardiac actin gene and the chicken gene for the alpha-subunit of the acetylcholine receptor were linked to the bacterial chloramphenicol acetyl transferase (CAT) gene and transfected into primary cultures derived from mouse skeletal muscle or into myogenic cell lines. We demonstrate that the mouse MLC1F/MLC3F gene has two functional promoters. In primary muscle cultures, a 1200 bp sequence flanking exon 1 (MLC1F) and a 438 bp sequence flanking exon 2 (MLC3F) direct CAT activity in myotubes, but not in myoblasts or in non myogenic 3T6 and CV1 cells. Developmentally regulated expression is also seen with the alpha-cardiac actin (320 bp) and acetylcholine receptor alpha-subunit (850 bp) upstream sequences in the primary culture system. Transfection experiments with myogenic cell lines show different results with a given promoter construct, reflecting possible differences in the levels of regulatory factors between lines. Different muscle gene promoters behave differently in a given cell line, suggesting different regulatory factor requirements between these promoters.

Actins↗
PubMed1988

Detection of the nicotinic acetylcholine receptor alpha-subunit mRNA by in situ hybridization at neuromuscular junctions of 15-day-old chick striated muscles.

In adult vertebrate striated muscle, the nicotinic acetylcholine receptor (AChR) is almost exclusively localized in the postsynaptic membrane of the neuromuscular junction. Using in situ hybridization, we show that, in two different chicken muscles [the slow multi-innervated anterior latissimus dorsi (ALD) and the fast singly innervated posterior latissimus dorsi (PLD)], the AChR alpha-subunit mRNA is detected at discrete regions on myofibres and that these regions co-localize (80% correspondence) with neuromuscular junctions identified by histochemical staining for acetylcholinesterase. Moreover, autoradiographic grains densely accumulate on and around subsynaptic nuclei. In contrast, hybridization with an actin probe results in a strong signal distributed over the entire length of the myofibres. Denervation increases the level of AChR alpha-subunit mRNA both in the PLD and to a lesser extent in the ALD. By in situ hybridization we observe that, although a perinuclear pattern is maintained, the labelled nuclei appear randomly distributed among approximately 10% of the nuclei. These results are discussed in a model of AChR gene expression in vertebrate striated muscle fibres.

Acetylcholinesterase↗
PubMed1988

Assignment of the human fast skeletal muscle myosin alkali light chains gene (MLC1F/MLC3F) to 2q 32.1-2qter.

A DNA probe derived from a mouse intronless pseudogene including coding regions for the myosin fast skeletal muscle alkali light chains, MLC1F/MLC3F (suggested HGM symbol, MYL1), was tested on a panel of 25 independent man-rodent somatic cell hybrids in order to assign the human MLC1F/MLC3F gene to a human chromosome. A 3.7-kb TaqI human fragment was found to correlate with the presence of chromosome 2 in the hybrids, characterized both by cytogenetic analysis and reference enzyme markers. A regional assignment to 2q32.1-qter was possible using hybrids whose human parental strains bore a reciprocal translocation t(X;2) (p22;q32.1). The fact that IDH1 and the MLC1F/MLC3F gene are closely linked on chromosome 1 in the mouse and map to the same region of human chromosome 2 in man indicates, that these chromosomes have a conserved region of homology between them and that the human 3.7-kb TaqI fragment corresponds indeed to a functional gene.

Animals↗
PubMed1988

Transcripts of alpha-cardiac and alpha-skeletal actins are early markers for myogenesis in the mouse embryo.

Among the first tissues to differentiate in the mammalian embryo are cardiac and subsequently skeletal striated muscle. We have developed specific cRNA probes corresponding to the 5' noncoding regions of alpha-cardiac and alpha-skeletal actin mRNAs in order to investigate myogenesis in the mouse embryo. Transcripts coding for cardiac actin which is the major isoform of the adult heart can first be detected between 7.5 and 7.8 days p.c. in the developing heart and are observed in all somites as they are formed. In addition, alpha-skeletal actin transcripts are accumulated at much lower levels in cardiac tissue and newly formed somites; both heart and skeletal muscle show co-expression of this actin gene pair at all stages of development examined. The fact that cardiac actin transcripts can be observed in the myotomal portion of the somite prior to muscle fibre differentiation indicates that cardiac actin transcripts (and to a lesser extent skeletal actin transcripts) are markers not only of striated muscle tissue, but also of earlier stages of the myogenic programme in vivo.

Actins↗
PubMed1987

Developmental pattern of mouse skeletal myosin heavy chain gene transcripts in vivo and in vitro.

We have studied the transcripts of the embryonic, perinatal, and adult fast myosin heavy chain (MHC) genes in mouse skeletal muscle in vivo before and after birth, and in vitro in myogenic cell lines. In vivo, in 15-day fetal muscle, embryonic and perinatal MHC mRNAs are both present, and the former is the major transcript. By 18 days the perinatal is predominant and the adult MHC mRNA appears. In beta-bungarotoxin-treated fetuses, a similar developmental pattern is detected, suggesting that it is nerve-independent and that primary myotubes alone undergo the same developmental changes. In vitro, in the absence of the nerve, embryonic, perinatal, and adult IIB MHC mRNAs accumulate. The level of the latter two isomRNAs is influenced by culture conditions.

Aging↗