Early Duplication of a Single MHC IIB Locus Prior to the Passerine Radiations

The myosin heavy chain (MHC) IIB gene is preferentially expressed in fast-twitch muscles of the hindlimb, such as the tibialis anterior (TA). The molecular mechanism(s) for this preferential expression are unknown. The goals of the current study were 1) to determine whether the cloned region of the MHC IIB promoter contains the necessary cis-acting element(s) to drive fiber-type-specific expression of this gene in vivo, 2) to determine which region within the promoter is responsible for fiber-type-specific expression, and 3) to determine whether transcription off of the cloned region of the MHC IIB promoter accurately mimics endogenous gene expression in a muscle undergoing a fiber-type transition. To accomplish these goals, a 2.6-kilobase fragment of the promoter-enhancer region of the MHC IIB gene was cloned upstream of the firefly luciferase reporter gene and coinjected with pRL-cytomegalovirus (CMV) (CMV promoter driving the renilla luciferase reporter) into the TA and the slow soleus muscle. Firefly luciferase activity relative to renilla luciferase activity within the TA was 35-fold greater than within the soleus. Deletional analysis demonstrated that only the proximal 295 base pairs (pGL3IIB0.3) were required to maintain this muscle-fiber-type specificity. Reporter gene expression of pGL3IIB0.3 construct was significantly upregulated twofold in unweighted soleus muscles compared with normal soleus muscles. Thus the region within the proximal 295 base pairs of the MHC IIB gene contains at least one element that can drive fiber-type-specific expression of a reporter gene.

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Habitat fragmentation in the Brazilian Atlantic Forest is associated with erosion of frog immunogenetic diversity and increased fungal infections

10.22541/au.161054186.64043009/v1 ◽

2021 ◽

Author(s):

Anat Belasen ◽

Kevin Amses ◽

Rebecca Clemons ◽

Guilherme Becker ◽

Felipe Toledo ◽

...

Keyword(s):

Habitat Fragmentation ◽

Atlantic Forest ◽

Batrachochytrium Dendrobatidis ◽

Fungal Infections ◽

Emerging Infectious Diseases ◽

Genetic Erosion ◽

Population Level ◽

Brazilian Atlantic Forest ◽

Frog Species ◽

Mhc Iib

Habitat fragmentation and infectious disease threaten amphibians globally, but little is known about how these two threats interact. In this study, we examined the effects of Brazilian Atlantic Forest habitat fragmentation on frog genetic diversity at an immune locus known to affect disease susceptibility in amphibians, the MHC IIB locus. We used a custom high-throughput assay to sequence the MHC IIB locus across six focal frog species in two regions of the Atlantic Forest. We also used a molecular assay to quantify infections by the fungal pathogen Batrachochytrium dendrobatidis (Bd). We found that habitat fragmentation is associated with genetic erosion at the MHC IIB locus, and that this erosion is most severe in frog species restricted to intact forests. Significant Bd infections were recovered only in one Atlantic Forest region, potentially due to the relatively higher elevation. In this region, forest specialists showed an increase in both Bd prevalence and loads in fragmented habitats. We also found that reduced population-level MHC IIB diversity was associated with increased Bd infection risk. On the individual-level, MHC IIB heterozygotes (by allelic genotype as well as supertype) exhibited a reduced risk of Bd infection. Our results suggest that habitat fragmentation increases infection susceptibility in amphibians, mediated at least in part through loss of immunogenetic diversity. Our findings have implications for the conservation of fragmented populations in the face of emerging infectious diseases.

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bHLH transcription factor MyoD affects myosin heavy chain expression pattern in a muscle-specific fashion

AJP Cell Physiology ◽

10.1152/ajpcell.2001.280.2.c408 ◽

2001 ◽

Vol 280 (2) ◽

pp. C408-C413 ◽

Cited By ~ 38

Author(s):

David J. Seward ◽

John C. Haney ◽

Michael A. Rudnicki ◽

Steven J. Swoap

Keyword(s):

Gene Expression ◽

Myosin Heavy Chain ◽

Heavy Chain ◽

Biceps Brachii ◽

Bhlh Transcription Factor ◽

Hindlimb Unweighting ◽

Protein Pool ◽

In The Wild ◽

Myod Gene ◽

Mhc Iib

A strong correlative pattern between MyoD gene expression and myosin heavy chain IIB (MHC IIB) gene expression exists. To test whether this correlative relationship is causative, MHC gene expression in muscles from MyoD(−/−) mice was analyzed. The MHC IIB gene was not detectable in the MyoD(−/−) diaphragm, whereas the MHC IIB protein made up 10.0 ± 1.7% of the MHC protein pool in the wild-type (WT) mouse diaphragm. Furthermore, the MHC IIA protein was not detectable in the MyoD(−/−) biceps brachii, and the MHC IIB protein was overexpressed in the masseter. To examine whether MyoD is required for the upregulation of the MHC IIB gene within slow muscle after disuse, MyoD(−/−) and WT hindlimb musculature was unweighted. MyoD(−/−) exhibited a diminished response in the upregulation of the MHC IIB mRNA within the soleus muscle as a result of the hindlimb unweighting. Collectively, these data suggest that MyoD plays a role in the MHC profile in a muscle-specific fashion.

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Influenza Infection has Fiber Type-Specific Effects on Cellular and Molecular Skeletal Muscle Function in Aged Mice

The Journals of Gerontology Series A ◽

10.1093/gerona/glaa136 ◽

2020 ◽

Vol 75 (12) ◽

pp. 2333-2341

Author(s):

Chad R Straight ◽

Olivia R Ringham ◽

Jenna M Bartley ◽

Spencer R Keilich ◽

George A Kuchel ◽

...

Keyword(s):

Skeletal Muscle ◽

Contractile Function ◽

Isometric Force ◽

Fiber Type ◽

Influenza Infection ◽

Fiber Types ◽

Specific Force ◽

Mhc Iia ◽

Mhc Iib ◽

Maximal Isometric Force

Abstract Skeletal muscle myopathies represent a common non-pulmonary manifestation of influenza infection, leading to reduced physical function and hospitalization in older adults. However, underlying mechanisms remain poorly understood. Our study examined the effects of influenza virus A pulmonary infection on contractile function at the cellular (single fiber) and molecular (myosin-actin interactions and myofilament properties) levels in soleus and extensor digitorum longus muscles of aged (20 months) C57BL/6 male mice that were healthy or flu-infected for 7 (7-days post-infection; 7-DPI) or 12 days (12-DPI). Cross-sectional area (CSA) of myosin heavy chain (MHC) IIA and IIB fibers was reduced at 12-DPI relative to 7-DPI and healthy. Maximal isometric force in MHC IIA fibers was also reduced at 12-DPI relative to 7-DPI and healthy, resulting in no change in specific force (maximal isometric force divided by CSA). In contrast, MHC IIB fibers produced greater isometric force and specific force at 7-DPI compared to 12-DPI or healthy. The increased specific force in MHC IIB fibers was likely due to greater myofilament lattice stiffness and/or an increased number or stiffness of strongly bound myosin-actin cross-bridges. At the molecular level, cross-bridge kinetics were slower in MHC IIA fibers with infection, while changes in MHC IIB fibers were largely absent. In both fiber types, greater myofilament lattice stiffness was positively related to specific force. This study provides novel evidence that cellular and molecular contractile function is impacted by influenza infection in a fiber type-specific manner, suggesting potential molecular mechanisms to help explain the impact of flu-induced myopathies.

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MHC-IIB Filament Assembly and Cellular Localization Are Governed by the Rod Net Charge

PLoS ONE ◽

10.1371/journal.pone.0001496 ◽

2008 ◽

Vol 3 (1) ◽

pp. e1496 ◽

Cited By ~ 21

Author(s):

Michael Rosenberg ◽

Ravid Straussman ◽

Ami Ben-Ya'acov ◽

Daniel Ronen ◽

Shoshana Ravid

Keyword(s):

Cellular Localization ◽

Net Charge ◽

Filament Assembly ◽

Mhc Iib

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Three-dimensional compartmentalization of myosin heavy chain and myosin light chain isoforms in dog thyroarytenoid muscle

AJP Cell Physiology ◽

10.1152/ajpcell.00323.2005 ◽

2006 ◽

Vol 290 (5) ◽

pp. C1446-C1458 ◽

Cited By ~ 14

Author(s):

Mark Bergrin ◽

Sabahattin Bicer ◽

Christine A. Lucas ◽

Peter J. Reiser

Keyword(s):

Myosin Heavy Chain ◽

Heavy Chain ◽

Light Chain ◽

Myosin Light Chain ◽

Expression Patterns ◽

Shortening Velocity ◽

Single Fibers ◽

Isoform Expression ◽

Thyroarytenoid Muscle ◽

Mhc Iib

The thyroarytenoid muscle, a vocal fold adductor, has important roles in airway protection (e.g., prevention of aspiration) and phonation. Isoform expression of myosin heavy chain (MHC), a major determinant of muscle-shortening velocity, has been reported to be heterogeneous in this muscle in several mammals, differing markedly between the medial and lateral divisions. The objective was to determine the isoform expression patterns of both MHC and myosin light chain (MLC), with the latter having a modulatory role in determining shortening velocity, to further test whether the expression of both myosin subunits differs in multiple specific sites within the divisions of the dog thyroarytenoid muscle, potentially revealing even greater compartmentalization in this muscle. Our results indicate the existence of large gradients in the relative levels of individual MHC isoforms in the craniocaudal axis along the medial layer (i.e., airflow axis), where levels of MHC-I and MHC-IIA are low at both ends of the axis and high in the middle and MHC-IIB has a reciprocal distribution. The lateral layer is more uniform, with high levels of MHC-IIB throughout. The level of MHC-IID is relatively constant along the axis in both layers. Large differences exist in the distribution of MHC isoforms among single fibers isolated from sites along the craniocaudal axis, especially in the lateral layer. Systematic regional variations are apparent in the MLC isoform composition of single fibers as well, including some MLC isoform combinations that are not observed in dog limb muscles. Variations of MHC and MLC isoform expression in the dog thyroarytenoid muscle are greater than previously recognized and suggest an even broader range of contractile properties within this multifunctional muscle.

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Two Regions of the Tail Are Necessary for the Isoform-specific Functions of Nonmuscle Myosin IIB

Molecular Biology of the Cell ◽

10.1091/mbc.e06-08-0706 ◽

2007 ◽

Vol 18 (3) ◽

pp. 1009-1017 ◽

Cited By ~ 24

Author(s):

Masaaki K. Sato ◽

Masayuki Takahashi ◽

Michio Yazawa

Keyword(s):

Heavy Chain ◽

Myosin Ii ◽

Nonmuscle Myosin ◽

Recognition Sites ◽

Self Recognition ◽

Nonmuscle Myosin Ii ◽

Exogenous Expression ◽

Mhc Iib ◽

C 63

To function in the cell, nonmuscle myosin II molecules assemble into filaments through their C-terminal tails. Because myosin II isoforms most likely assemble into homo-filaments in vivo, it seems that some self-recognition mechanisms of individual myosin II isoforms should exist. Exogenous expression of myosin IIB rod fragment is thus expected to prevent the function of myosin IIB specifically. We expected to reveal some self-recognition sites of myosin IIB from the phenotype by expressing appropriate myosin IIB rod fragments. We expressed the C-terminal 305-residue rod fragment of the myosin IIB heavy chain (BRF305) in MRC-5 SV1 TG1 cells. As a result, unstable morphology was observed like MHC-IIB−/− fibroblasts. This phenotype was not observed in cells expressing BRF305 mutants: 1) with a defect in assembling, 2) lacking N-terminal 57 residues (N-57), or 3) lacking C-terminal 63 residues (C-63). A myosin IIA rod fragment ARF296 corresponding to BRF305 was not effective. However, the chimeric ARF296, in which the N-57 and C-63 of BRF305 were substituted for the corresponding regions of ARF296, acquired the ability to induce unstable morphology. We propose that the N-57 and C-63 of BRF305 are involved in self-recognition when myosin IIB molecules assemble into homo-filament.

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An E-box within the MHC IIB gene is bound by MyoD and is required for gene expression in fast muscle

AJP Cell Physiology ◽

10.1152/ajpcell.1999.276.5.c1069 ◽

1999 ◽

Vol 276 (5) ◽

pp. C1069-C1078 ◽

Cited By ~ 131

Author(s):

Matthew T. Wheeler ◽

Emily C. Snyder ◽

Melissa N. Patterson ◽

Steven J. Swoap

Keyword(s):

Gene Expression ◽

Reporter Gene ◽

Soleus Muscle ◽

Time Course ◽

De Novo ◽

Hindlimb Suspension ◽

Causative Role ◽

Dependent Manner ◽

E Box ◽

Mhc Iib

The myosin heavy chain (MHC) IIB gene is selectively expressed in skeletal muscles, imparting fast contractile kinetics. Why the MHC IIB gene product is expressed in muscles like the tibialis anterior (TA) and not expressed in muscles like the soleus is currently unclear. It is shown here that the mutation of an E-box within the MHC IIB promoter decreased reporter gene activity in the fast-twitch TA muscle 90-fold as compared with the wild-type promoter. Reporter gene expression within the TA required this E-box for activation of a heterologous construct containing upstream regulatory regions of the MHC IIB promoter linked to the basal 70-kDa heat shock protein TATA promoter. Electrophoretic mobility shift assays demonstrated that mutation of the E-box prevented the binding of both MyoD and myogenin to this element. In cotransfected C2C12myotubes and Hep G2 cells, MyoD preferentially activated the MHC IIB promoter in an E-box-dependent manner, whereas myogenin activated the MHC IIB promoter to a lesser extent, and in an E-box-independent manner. A time course analysis of hindlimb suspension demonstrated that the unweighted soleus muscle activated expression of MyoD mRNA before the de novo expression of MHC IIB mRNA. These data suggest a possible causative role for MyoD in the observed upregulation of MHC IIB in the unweighted soleus muscle.

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Fiber type effects on contraction-stimulated glucose uptake and GLUT4 abundance in single fibers from rat skeletal muscle

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00466.2014 ◽

2015 ◽

Vol 308 (3) ◽

pp. E223-E230 ◽

Cited By ~ 13

Author(s):

Carlos M. Castorena ◽

Edward B. Arias ◽

Naveen Sharma ◽

Jonathan S. Bogan ◽

Gregory D. Cartee

Keyword(s):

Skeletal Muscle ◽

Glucose Uptake ◽

Glucose Transporter ◽

Fiber Type ◽

Fiber Types ◽

Rat Skeletal Muscle ◽

Single Fibers ◽

Mhc Iia ◽

Mhc Iib ◽

Filamin C

To fully understand skeletal muscle at the cellular level, it is essential to evaluate single muscle fibers. Accordingly, the major goals of this study were to determine if there are fiber type-related differences in single fibers from rat skeletal muscle for: 1) contraction-stimulated glucose uptake and/or 2) the abundance of GLUT4 and other metabolically relevant proteins. Paired epitrochlearis muscles isolated from Wistar rats were either electrically stimulated to contract (E-Stim) or remained resting (No E-Stim). Single fibers isolated from muscles incubated with 2-deoxy-d-[3H]glucose (2-DG) were used to determine fiber type [myosin heavy chain (MHC) isoform protein expression], 2-DG uptake, and abundance of metabolically relevant proteins, including the GLUT4 glucose transporter. E-Stim, relative to No E-Stim, fibers had greater ( P < 0.05) 2-DG uptake for each of the isolated fiber types (MHC-IIa, MHC-IIax, MHC-IIx, MHC-IIxb, and MHC-IIb). However, 2-DG uptake for E-Stim fibers was not significantly different among these five fiber types. GLUT4, tethering protein containing a UBX domain for GLUT4 (TUG), cytochrome c oxidase IV (COX IV), and filamin C protein levels were significantly greater ( P < 0.05) in MHC-IIa vs. MHC-IIx, MHC-IIxb, or MHC-IIb fibers. TUG and COX IV in either MHC-IIax or MHC-IIx fibers exceeded values for MHC-IIxb or MHC-IIb fibers. GLUT4 levels for MHC-IIax fibers exceeded MHC-IIxb fibers. GLUT4, COX IV, filamin C, and TUG abundance in single fibers was significantly ( P < 0.05) correlated with each other. Differences in GLUT4 abundance among the fiber types were not accompanied by significant differences in contraction-stimulated glucose uptake.

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