Biomedical subjects

C Chassagne

Publications and source records attributed to C Chassagne.

23 records · Page 2Linked to original sources

PubMed1992

Cardiac expressions of alpha- and beta-myosin heavy chains and sarcomeric alpha-actins are regulated through transcriptional mechanisms. Results from nuclear run-on assays in isolated rat cardiac nuclei.

In the heart, mRNA accumulations for sarcomeric actins and myosin heavy chains (MHC) are subject to diverse regulatorial processes. To study cardiac contractile protein transcriptional regulations, an in vitro transcription system using nonenzymatically isolated rat cardiac nuclei was characterized. Transcription was shown to be rapid and continuous during the first 20 min of incubation and 5.4-fold less than that seen from comparably isolated hepatocyte nuclei. Neither RNase nor DNase activities were detectable. Direct transcriptional analyses of the alpha- and beta-MHC and cardiac and skeletal alpha-actin genes from cardiac nuclei were performed. In 23-24-day-old rats, significant levels of transcription were seen for alpha-MHC and for the sarcomeric alpha-actins. beta-MHC was just detectable, and no positive signals were ever seen for fibronectin. We then compared the perecentages of MHC and sarcomeric alpha-actin expressions determined from 1) the transcriptional assays and 2) total isolated RNA (alpha-MHC: 90.1 +/- 4.8% (transcription), 93.0 +/- 4.7% (accumulation); beta-MHC: 9.9 +/- 4.8%, 7.0 +/- 4.7%; cardiac alpha-actin: 84.0 +/- 2.5%, 84.9 +/- 2.5%; skeletal alpha-actin: 16.1 +/- 2.5%, 15.0 +/- 2.5%). The results support the conclusion that the primary mechanisms controlling the accumulations of these gene products are transcriptional. Additionally, we show that an anti-sense mRNA showing strong homology or identity with the 5' end of the beta-MHC gene is transcribed in cardiac nuclei but not in hepatocyte nuclei.

Actins↗

PubMed1992

Expression of the sarcomeric actin isogenes in the rat heart with development and senescence.

Sarcomeric actin genes, alpha-cardiac and alpha-skeletal, are coexpressed in neonatal rodent hearts and are regulated in response to hormonal and hemodynamic stimuli; however, their precise developmental pattern of expression has not been determined, and it is unknown whether they are coexpressed during senescence. We have, therefore, investigated the accumulation of sarcomeric actin transcripts in rat heart during fetal and postnatal development and with senescence by two different techniques: primer extension analysis with an oligonucleotide common to both sarcomeric actins and RNA hybridization with specific cardiac alpha-actin cRNA probes. We found that at 17-19 days in utero both isogenes are coexpressed and alpha-skeletal actin mRNAs represent 28.0 +/- 0.8% of the sarcomeric actin mRNA total. Skeletal actin mRNAs increase to 40% of the total 1 week after birth (NS, p = 0.15), remain constant for 3 weeks, and decrease to less than 20% of the total in ventricles and atria of 1-month-old rats. The alpha-skeletal actin transcripts further decline to less than 5% of the total at 2 months of age and do not reaccumulate in senescent animals. There was no significant difference between male and female rat ventricles. By comparison with the known accumulations of alpha- and beta-myosin heavy chain mRNAs, our results demonstrate that whatever the developmental stage the kinetics of expression for the sarcomeric myosin and actin multigene families are independent.

Actins↗

PubMed1992

Regulation of myosin heavy chain and actin isogenes during cardiac growth and hypertrophy.

Expression of myosin heavy chain (MHC) and actin multigene families changes in mammals during cardiac growth and hypertrophy, but whether or not there is a common regulatory pathway is unclear. To address this question, we have looked at the alpha- and beta-MHC, and at the alpha-skeletal and alpha-cardiac actin (alpha-skel act and alpha-card act) isomRNA transitions during development and senescence, both in rat and human hearts. Since the precise amounts of each isoactin mRNA were not precisely known in the above situations, we first analyzed the time- course of accumulations of the two sarcomeric transcripts by primer extension assays, which allow an umambiguous quantification of the ratios of the two actin transcripts. In rats, both isogenes are expressed in-utero. alpha-skel act represents 40% of the total one week after birth, remains constant for 3 weeks, decreases to less than 5% at two months and does not re-accumulate thereafter. In humans, in contrast, alpha-skel act represents < 20% in-utero and in neonates, increases to 48% during the first decade after birth and becomes the predominant isoform of adult hearts. In rats beta-MHC mRNAs accumulate at birth, become undetectable at 3 weeks and reaccumulate to as much as 80% during senescence, and in humans beta-MHC mRNAs predominate throughout all developmental stages. These data show that in both species, the multigene families encoding the major contractile proteins are not coordinately regulated during development and aging.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗

PubMed1991

[Improvement of an in vitro transcription method in nuclei isolated from heart myocytes from control and hemodynamically overloaded rats].

The expression of genes crucial for different cardiac functions changes during ontogenic development and during hypertrophy due to hemodynamic overload. To determine if these changes are transcriptional or post-transcriptional, we describe here an optimized method to analyze in vitro the transcriptional activity of nuclei isolated from control and hemodynamically overloaded hearts of 23-day-old rats. Similar results were obtained with both types of hearts: (1) 3 to 6 million nuclei were isolated per gram of ventricular tissue; (2) nuclear incorporation of UTP32P increases with time, plateaus after about 10 to 20 min. and attains an average of 0.17 cpm per nucleus; (3) alpha-amanitin decreases total incorporation by 56%; (4) the sizes of the majority of transcribed RNA are between 0.2 and 4 kb, although a significant fraction of high molecular weight transcripts are also seen (between 4 and 6 kb). All this indicates that mRNAs are transcribed to a significant extent, suggesting that it is now possible, given appropriate nucleotide probes, to analyze the transcription of any given gene during cardiac growth.

Animals↗

PubMedDate not supplied

Regulation of myosin heavy chain and actin isogenes expression during cardiac growth.

The cardiac ventricular myosin heavy chain phenotype is developmentally and hormonally regulated, but less is known concerning the actin phenotype. In this study, the levels of accumulation of alpha-skeletal and alpha-cardiac actin mRNAs were investigated in rat and human ventricles by primer extension assays. In rat, the two iso-mRNAs are present in approximately equal amounts from birth until 15 days of age and the cardiac form is predominant in adult and senescent hearts. Hypothyroid development has no effect, at least during the first two weeks of age. In man, the two isoactins are co-expressed to similar ratios in one control heart and in one failing heart. It therefore appears that myosin heavy chain and actin multigene families are both expressed in a species specific fashion but are independently regulated within a species. Preliminary results from nuclear run-on assays are presented that indicate differences in the level of transcription of the alpha-actin and beta-myosin heavy chain isogenes in the rat heart.

Actins↗