Identification of three developmentally controlled isoforms of human myosin heavy chains

Single nucleotide polymorphisms, haplotypes and combined genotypes in MYH₃ gene and their associations with growth and carcass traits in Qinchuan cattle

MYH₃ is a major contractile protein which converts chemical energy into mechanical energy through the ATP hydrolysis. MYH₃ is mainly expressed in the skeletal muscle in different stages especially embryonic period, and it has a role in the development of skeletal muscle and heart. In this study, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was applied to analyze the genetic variations of the MYH₃ gene and verify the effect on growth and carcass traits in a total of 365 Qinchuan cattles. The PCR product was digested with some restriction enzyme and demonstrated the polymorphism in the population, the single nucleotide polymorphisms (SNPs) at nucleotides g. +1215T>C, g. +3377C>T, and g. +28625C>T were in linkage disequilibrium with each other. The result of haplotype analysis showed that nineteen different haplotypes were identified among the five SNPs. The statistical analyses indicated that the five SNPs were significant association with growth and carcass traits (P < 0.05, N = 365); whereas the five SNPs were no significant association between 18 combined genotypes of MYH₃ gene and growth and carcass traits. Taken together, our results provide the evidence that polymorphisms in MYH₃ are associated with growth and carcass traits in Qinchuan cattle, and may be used as a possible candidate for marker-assisted selection and management in beef cattle breeding program.

Premature expression of a muscle fibrosis axis in chronic HIV infection

Background

Despite the success of highly active antiretroviral therapy (HAART), HIV infected individuals remain at increased risk for frailty and declines in physical function that are more often observed in older uninfected individuals. This may reflect premature or accelerated muscle aging.

Methods

Skeletal muscle gene expression profiles were evaluated in three uninfected independent microarray datasets including young (19 to 29 years old), middle aged (40 to 45 years old) and older (65 to 85 years old) subjects, and a muscle dataset from HIV infected subjects (36 to 51 years old). Using Bayesian analysis, a ten gene muscle aging signature was identified that distinguished young from old uninfected muscle and included the senescence and cell cycle arrest gene p21/Cip1 (CDKN1A). This ten gene signature was then evaluated in muscle specimens from a cohort of middle aged (30 to 55 years old) HIV infected individuals. Expression of p21/Cip1 and related pathways were validated and further analyzed in a rodent model for HIV infection.

Results

We identify and replicate the expression of a set of muscle aging genes that were prematurely expressed in HIV infected, but not uninfected, middle aged subjects. We validated select genes in a rodent model of chronic HIV infection. Because the signature included p21/Cip1, a cell cycle arrest gene previously associated with muscle aging and fibrosis, we explored pathways related to senescence and fibrosis. In addition to p21/Cip1, we observed HIV associated upregulation of the senescence factor p16INK4a (CDKN2A) and fibrosis associated TGFβ1, CTGF, COL1A1 and COL1A2. Fibrosis in muscle tissue was quantified based on collagen deposition and confirmed to be elevated in association with infection status. Fiber type composition was also measured and displayed a significant increase in slow twitch fibers associated with infection.

Conclusions

The expression of genes associated with a muscle aging signature is prematurely upregulated in HIV infection, with a prominent role for fibrotic pathways. Based on these data, therapeutic interventions that promote muscle function and attenuate pro-fibrotic gene expression should be considered in future studies.

cDNA cloning and characterization of temperature-acclimation-associated light meromyosins from grass carp fast skeletal muscle

The three types of cDNA clones, previously defined as the 10 degrees C, intermediate and 30 degrees C-types [Tao, Y., Kobayashi, M., Liang, C.S., Okamoto, T., Watabe, S., 2004. Temperature-dependent expression patterns of grass carp fast skeletal myosin heavy chain genes. Comp. Biochem. Physiol. B 139, 649-656], were determined for their 5'-regions which encoded at least the C-terminal half of myosin rod, light meromyosin (LMM), in fast skeletal muscles of grass carp Ctenopharyngodon idella. The deduced amino acid sequence identity was 91.1% between the 10 degrees C and 30 degrees C-types and 91.4% between the 10 degrees C and intermediate-types, whereas a high sequence identity of 97.8% was found between the intermediate and 30 degrees C-types. These three grass carp LMMs all had a characteristic seven-residue (heptad) repeat (a, b, c, d, e, f, g)(n), where positions a and d were normally occupied by hydrophobic residues, and positions b, c and f by charged residues. However, the ratios of hydrophobic residues to the total were higher for the intermediate- and 30 degrees C- than 10 degrees C-type LMM, suggesting that the former both types may form more stable coiled-coils of alpha-helices than the latter type. These differences in the primary structures of LMM isoforms might be partially implicated in differences in the thermostabilities and gel-forming profiles of myosins from grass carp in different seasons reported previously [Tao, Y., Kobayashi, M., Fukushima, H., Watabe, S., 2005. Changes in enzymatic and structural properties of grass carp fast skeletal myosin induced by the laboratory-conditioned thermal acclimation and seasonal acclimatization. Fish. Sci. 71, 195-204; Tao, Y., Kobayashi, M., Fukushima, H., Watabe, S., 2007. Changes in rheological properties of grass carp fast skeletal myosin induced by seasonal acclimatization. Fish. Sci. 73, 189-196].

Characterization of the carp myosin heavy chain multigene family

We isolated partial coding sequences for 29 carp myosin heavy chain genes (MyoHCs) and determined the nucleotide sequences around the region encoding the loop 2 of the myosin molecule. The predicted amino acid sequences from the isolated genes all showed very high similarity to those of skeletal and cardiac muscles from higher vertebrates, but not to those of smooth and non-muscle counterparts. Among all clones isolated, carp MyoHC10, MyoHCI-1-3 and MyoHC30 showed exon-nucleotide sequences identical to those of cDNAs encoding the loop 2 region of the 10 degrees C-, intermediate- and 30 degrees C-type fast skeletal isoforms [Hirayama and Watabe, Euro. J. Biochem. 246 (1997) 380-387]. The loop 2 of 28 types of carp MyoHCs was encoded by two exons separated by an intron corresponding to that of the 16th in higher vertebrate MyoHCs, whilst this intron was not found in carp MyoHC30. Although carp MyoHC30 had a gene organization different from those of higher vertebrates and other carp MyoHCs, its predicted amino acid sequence for loop 2 showed the highest homology to those of higher vertebrates among carp MyoHCs. In the 28 carp MyoHCs containing the intron, a combination of different nucleotide sequences for the two resulted in 14 distinct series for the combined coding sequence. These different nucleotide sequences encoded nine distinct amino acid sequences. Phylogenetic analysis for the present loop 2 and light meromyosin previously reported for carp MyoHCs [Imai et al., J. Exp. Biol. 200 (1997) 27-34] revealed that carp MyoHCs have recently diverged and are more closely related to each other than to MyoHCs from other species.

Activation of the Lbc Rho exchange factor proto-oncogene by truncation of an extended C terminus that regulates transformation and targeting

The human lbc oncogene product is a guanine nucleotide exchange factor that specifically activates the Rho small GTP binding protein, thus resulting in biologically active, GTP-bound Rho, which in turn mediates actin cytoskeletal reorganization, gene transcription, and entry into the mitotic S phase. In order to elucidate the mechanism of onco-Lbc transformation, here we report that while proto- and onco-lbc cDNAs encode identical N-terminal dbl oncogene homology (DH) and pleckstrin homology (PH) domains, proto-Lbc encodes a novel C terminus absent in the oncoprotein that includes a predicted alpha-helical region homologous to cyto-matrix proteins, followed by a proline-rich region. The lbc proto-oncogene maps to chromosome 15, and onco-lbc represents a fusion of the lbc proto-oncogene N terminus with a short, unrelated C-terminal sequence from chromosome 7. Both onco- and proto-Lbc can promote formation of GTP-bound Rho in vivo. Proto-Lbc transforming activity is much reduced compared to that of onco-Lbc, and a significant increase in transforming activity requires truncation of both the alpha-helical and proline-rich regions in the proto-Lbc C terminus. Deletion of the chromosome 7-derived C terminus of onco-Lbc does not destroy transforming activity, demonstrating that it is loss of the proto-Lbc C terminus, rather than gain of an unrelated C-terminus by onco-Lbc, that confers transforming activity. Mutations of onco-Lbc DH and PH domains demonstrate that both domains are necessary for full transforming activity. The proto-Lbc product localizes to the particulate (membrane) fraction, while the majority of the onco-Lbc product is cytosolic, and mutations of the PH domain do not affect this localization. The proto-Lbc C-terminus alone localizes predominantly to the particulate fraction, indicating that the C terminus may play a major role in the correct subcellular localization of proto-Lbc, thus providing a mechanism for regulating Lbc oncogenic potential.

Endomyocardial gene expression during development of pacing tachycardia-induced heart failure in the dog

Selective and specific changes in gene expression characterize the end-stage failing heart. However, the pattern and relation of these changes to evolving systolic and diastolic dysfunction during development of heart failure remains undefined. In the present study, we assessed steady-state levels of mRNAs encoding a group of cardiac proteins during the early development of left ventricular dysfunction in dogs with pacing-induced cardiomyopathy. Corresponding hemodynamic assessments were made in the conscious state in the same animals and at the same time points at baseline, after 1 week of ventricular pacing, and at the onset of clinical heart failure. Systolic dysfunction dominated after 1 week of pacing, whereas diastolic dysfunction was far more pronounced with the onset of heart failure. Atrial natriuretic factor mRNA was undetectable in 7 of 12 hearts at baseline but was expressed in all hearts at 1 week (P < .01 by chi 2 test), and it increased markedly with progression to failure (P = .05). Creatine kinase-B mRNA also rose markedly with heart failure (P < .01). Levels of mRNA encoding beta-myosin heavy chain, mitochondrial creatine kinase, phospholamban, and sarcoplasmic reticulum Ca(2+)-ATPase did not significantly change from baseline, despite development of heart failure. Additional analysis to determine if these mRNA changes were related to the severity of diastolic or systolic dysfunction revealed that phospholamban mRNA decreased in hearts with larger net increases in end-diastolic pressure (+19.2 +/- 1.9 mm Hg) compared with those hearts in which it did not change (+4.0 +/- 4.9, P < .02).(ABSTRACT TRUNCATED AT 250 WORDS)

Myosin polymorphism and differential expression in adult human skeletal muscle

1. Myosin heavy chain (HC) and light chain (LC) isoforms are expressed in a tissue-specific and developmentally-regulated manner in human skeletal muscle. 2. At least seven myosin HC isoforms are expressed in skeletal muscle of the adult. 3. Histochemically-delineated fibre types (based on the stability of myofibrillar actomyosin adenosine triphosphatase activity) in limb muscles correlate with the myosin HC content. 4. Alterations in the phenotypic expression of myosin provides a mechanism of adaptation to stresses placed upon the muscle (e.g. increased and decreased usage).

Developmental modulation of myocardial mechanics: age- and growth-related alterations in afterload and contractility

Somatic growth is associated with alterations in myocardial mechanics in children with heart disease and in most animal models of congenital heart disease. However, the effect of age and body size on myocardial contractility and loading conditions in normal infants and children is not known. Therefore, 256 normal children aged 7 days to 19 years (34% less than 3 years old) were evaluated with noninvasive indexes of left ventricular contractility and loading conditions. Two-dimensional and M-mode echocardiographic recordings of the left ventricle were obtained with a phonocardiogram, indirect pulse tracing and blood pressure recordings. Left ventricular dimensions, wall thickness and pressure measurements obtained from these data were used to calculate peak and end-systolic circumferential and meridional wall stress and mean and integrated meridional wall stress. Velocity of shortening adjusted for heart rate was compared with end-systolic stress to assess contractility independently of loading status. The subjects were stratified for gender and each of the derived variables was related to age and body surface area. Ventricular shape, assessed as the major/minor axis ratio, and the circumferential/meridional stress ratio were found to be invariant with growth. The ratio of posterior wall thickness to minor axis dimension did not change with age, despite the normal age-related increase in blood pressure. The increase in pressure despite unvarying ventricular shape and wall thickness/dimension ratio resulted in a substantial increase in wall stress that was most dramatic during the first few years of life. In association with the increase in afterload, systolic function decreased with age. However, the age-related decrease in the velocity of shortening was greater than that expected from the increase in afterload alone, indicating a higher level of contractility in infants and children during the first years of life than in older subjects. The process of normal growth and development, similar to that in children with heart disease, is associated with a rapid decrease in the trophic response to hemodynamic loads, resulting in an age-associated increase in wall stress. There is a similar but somewhat more rapid decrease in contractility, with the highest values seen in the youngest patients.

Structural and functional diversity of human ventricular myosin

The role of subcellular alterations in the process of heart failure remains ill-defined. Because contractile performance of failing heart muscle is depressed, possible alterations in the myosin molecule could be of particular relevance. There is increasing evidence that myofibrillar ATPase activity is reduced in congestive heart failure, whereas the findings on myosin ATPase are still controversial. The molecular causes of the reduced activity are currently not known. Because alpha-MHC is present only in small amounts in normal ventricles, a shift in favor of beta-MHC is of minor importance. Also immunohistochemical data on subspecies of beta-MHC seem not to provide an explanation. A new type of myosin heterogeneity was found by optimizing native polyacrylamide gel electrophoresis in the presence of pyrophosphate. Two bands (VA and VB) were observed in ventricles of patients with valvular disease. Because the two bands were detected also in normal hearts of large mammals, the existence of VA/VB cannot be diagnostic of diseased heart. However, the VA/VB ratio was influenced by the hemodynamic load, whereby the fast migrating band (VA) increased with the diastolic and systolic load. Because a relationship with the hemodynamic load was observed only in surgical muscle specimens, it appears that this heterogeneity is prone to post mortem modification. Further work is required to identify the molecular nature of this heterogeneity and to examine the therapeutic potential of a pharmacological modification of the VA/VB ratio.

Structural and phylogenetic analysis of the chicken ventricular myosin heavy chain rod

We have isolated and characterized five overlapping clones that encompass 3.2 kb and encode a part of the short subfragment 2, the hinge, and the light meromyosin regions of the myosin heavy chain rod as well as 143 bp of the 3' untranslated portion of the mRNA. Northern blot analysis showed expression of this mRNA mainly in ventricular muscle of the adult chicken heart, with trace levels detected in the atrium. Transient expression was seen in skeletal muscle during development and in regenerating skeletal muscle following freeze injury. To our knowledge, this is the first report of an avian ventricular myosin heavy chain sequence. Phylogenetic analysis indicated that this isoform is a distant homolog of other ventricular and skeletal muscle myosin heavy chains and represents a distinct member of the multigene family of sarcomeric myosin heavy chains. The ventricular myosin heavy chain of the chicken is either paralogous to its counterpart in other vertebrates or has diverged at a significantly higher rate.