ProfessorOffice: Anatomy/Zoology Building E345Phone: 970-491-7616Website: http://rydberg.biology.colostate.edu/mykleslabEducation: Ph.D., University of California, BerkeleyEmail: Donald.Mykles@ColoState.EDU
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Our research concerns the regulation of molting and skeletal muscle plasticity in crabs and lobsters. Specific areas are signaling mechanisms in the molting gland and proteolytic mechanisms mediating molt-induced claw muscle atrophy. Quantitative methods are used to measure transcriptional and post-transcriptional regulation of signal transduction of molt-inhibiting hormone (MIH), a neuropeptide that inhibits ecdysteroid synthesis in the molting gland and myostatin, a TGFß superfamily member that induces skeletal muscle atrophy.
Signaling mechanisms in crustacean molting gland. Growth in crustaceans requires the periodic shedding of the shell, a process called molting, which is controlled by a neurosecretory center in the eyestalks. The complex secretes MIH that inhibits production of the molting hormone ecdysone, an ecdysteroid secreted by a pair of molting glands (Y-organs or YOs) located in the body. Thus molting is triggered by a reduction in MIH in the blood, which stimulates the YOs to synthesize and secrete ecdysone. Binding of MIH to a membrane receptor results in a cyclic nucleotide-dependent inhibition of mechanistic Target of Rapamycin (mTOR), a highly conserved protein kinase that controls protein synthesis. The YO transitions to a committed state during premolt that requires TGFß signaling. Transcriptomics and proteomics are being used to understand the genetic mechanisms of YO transitions during the molt cycle.
Regulation of muscle atrophy by myostatin. In mammals myostatin (Mstn) is a negative regulator skeletal muscle growth. We hav identified Mstn orthologs in crabs and lobsters. As these genes are preferentially expressed in skeletal muscle, they may have similar functions in invertebrates. We are examining the role of Mstn in controlling molt-induced claw muscle atrophy, in which the claw muscle mass is reduced as much as 78% before molting. The reduced mass facilitates withdrawal of the large claws through the narrow joints that connect the appendage to the body. Binding of Mstn to a membrane receptor results in phosphorylation of Smad proteins. Smads are transcription factors that translocate to the nucleus and alter gene expression. cDNAs encoding land crab Smads have been obtained. Quantitative RT-PCR and proteomic analysis are used to measure Smad mRNA and protein levels, respectively. Image analysis are used to quantify Smads in the nucleus and cytoplasm in response to Mstn.
Jeon, J.-M., Kim, B.-K., Oh, C.-W., Lee, J. H., Kim, H. J., Kang, C.-K., Mykles, D. L., and Kim, H.-W. (2012). Molecular characterization of two type I crustacean hyperglycemic hormone (CHH) genes in Morotoge shrimp (Pandalopsis japonica): cloning and expression of eyestalk and pericardial organ isoforms produced by alternative splicing and a novel type I CHH with predicted structure shared with type II CHH peptides. Comp Biochem. Physiol 162B:88-99.
Silverman-Gavrila, L. B., Praver, M., Mykles, D. L., and Charlton, M. P. (2013). Calcium, calpain, and calcineurin in low-frequency depression of transmitter release. J. Neurosci. 33:1975-1990.
MacLea, K. S., Abuhagr, A. M., Pitts, N. L., Covi, J. A., Bader, B. D., Chang, E. S., and Mykles, D. L. (2012). Rheb, an activator of target of rapamycin, in the blackback land crab, Gecarcinus lateralis: cloning and effects of molting and unweighting on expression in skeletal muscle. J. Exp. Biol. 215: 590-604.
Covi, J. A., Chang, E. S., and Mykles, D. L. (2012). Neuropeptide signaling mechanisms in crustacean and insect molting glands. Invert. Reprod. Dev. 56: 33-49.
Mykles, D. L. (2011). Ecdysteroid metabolism in crustaceans. J. Steroid Biochem. Molec. Biol. 127:196-203.
Chang, E. S., and Mykles, D. L. (2011). Regulation of crustacean molting: A review and our perspectives. Gen. Comp. Endocrinol. 172:323-330.
McDonald, A. A., Chang, E. S., and Mykles, D. L. (2011). Cloning of a nitric oxide synthase from green shore crab, Carcinus maenas: a comparative study of the effects of eyestalk ablation on expression in the molting glands (Y-organs) of C. maenas, and blackback land crab, Gecarcinus lateralis. Comp. Biochem. Physiol. 158A: 150-162.
Lee, S.-O., Jeon, J.-M., Oh, C.-W., Kim, Y. M., Kang, C.-K., Lee, D.-S., Mykles, D. L., and Kim, H.-W. (2011). Two juvenile hormone esterase-like carboxylesterase cDNAs from a Pandalus shrimp (Pandalopsis japonica): cloning, tissue expression, and effects of eyestalk ablation. Comp. Biochem. Physiol. 159B:148-156.
MacLea, K., Covi, J. A., Chao, E., Kim, H.-W, Medler, S., Chang, E. S., and Mykles, D. L. (2010). Myostatin from the American lobster, Homarus americanus: cloning and effects of molting on expression in skeletal muscles. Comp. Biochem. Physiol. 157A:328-337.
Mykles, D. L., Adams, M. E., Gäde, G., Lange, A. B., Marco, H. G., and Orchard, I. (2010) Neuropeptide action in insects and crustaceans. Physiol. Biochem. Zool. 83:836-846.
Chao, E., Kim, H.-W., and Mykles, D. L. (2010). Cloning and tissue expression of eleven troponin-C isoforms in the American lobster, Homarus americanus. Comp. Biochem. Physiol. 157B:88-101.
Jeon, J.-M. Lee, S.-O., Kim, K. S., Baek, H.-J., Kim, I.-K., Mykles, D. L., and Kim, H.-W. (2010) Characterization of two vitellogenin cDNAs from a Pandalus shrimp (Pandalopsis japonica): expression in hepatopancreas is down-regulated by endosulfan exposure. Comp. Biochem. Physiol. 157B:102-112.
Mykles, D. L., Ghalambor, C. K., Stillman, J. H., and Tomanek, L. (2010). Grand challenges in comparative physiology: Integration across disciplines and across levels of biological organization. Integr. Comp. Biol. 50:6-16.
Covi, J. A., Bader, B.D., Chang, E. S., and Mykles, D. L. (2010) Molt cycle regulation of protein synthesis in skeletal muscle of the blackback land crab, Gecarcinus lateralis, and the differential expression of a myostatin-like factor during atrophy induced by molting or unweighting. J. Exp. Biol. 213:172-183.
Kim, B. K., Kim, K. S., Oh, C. -W., Mykles, D. L., Lee, S.G., Kim, H.J., and Kim, H.-W. (2009) Twelve actin-encoding cDNAs from the American lobster, Homarus americanus: cloning and tissue expression of eight skeletal muscle, one heart, and three cytoplasmic isoforms. Comp. Biochem. Physiol. 153B: 178-184.
Covi, J. A., Chang, E. S., and Mykles, D. L. (2009) Conserved role of cyclic nucleotides in the regulation of ecdysteroidogenesis by the crustacean molting gland. Comp. Biochem. Physiol. 152A:470-477.
Zarubin, T. P., Chang, E. S., and Mykles, D. L. (2009) Expression of recombinant eyestalk crustacean hyperglycemic hormone from the tropical land crab, Gecarcinus lateralis, that inhibitsY-organ ecdysteroidogenesis in vitro. Mol. Biol. Rep. 36: 1231-1237.
Covi, J., Gomez, A., Chang, S., Lee, K., Chang, E., and Mykles, D. (2008). Repression of Y-organ ecdysteroidogenesis by cyclic nucleotides and agonists of NO-sensitive guanylyl cyclase. In: 4th Meeting of Comparative Physiologists & Biochemists in Africa - Mara 2008 - "Molecules to Migration: The Pressures of Life", Morris S. and Vosloo, A., eds. Medimond S.r.l., Monduzzi Editore International, Bologna, Italy, pp. 37-46.
Covi, J. A., Kim, H.-W., and Mykles, D. L. (2008) Expression of alternatively spliced transcripts for a myostatin-like protein in the blackback land crab, Gecarcinus lateralis. Comp. Biochem. Physiol. 150A:423-430.
Medler, S., E.S. Change and D.L. Mykles. 2007. Muscle-specific calpain is localized in regions near motor endplates in differentiating lobster claw muscles. Comp. Biochem. Physiol. 148A:591-598.
Lee, S.G., H.-W. Kim and D.L. Mykles. 2007. Guanylyl cyclases in the tropical land crab: Gecarcinus lateralis: cloning of soluble (NO-sensitive and -insensitive) and membrane receptor forms. Comp. Biochem. Physiol. 2D:332-344.
Lee, S. G., B. D. Bader, E.S. Chang and D.L. Mykles. 2007. Effects of elevated ecdysteriod on tissue expression of three guanylyl cyclases in the tropical land crab, Gecarcinus lateralis: possible roles of neuropeptide signaling in the molting gland. J. Exp. Biol. 210:3245-3254.
Lee, K.J., R.M. Doran and D.L. Mykles. 2007. Crustacean hyperglycemic hormone from the tropical land crab, Gecarcinus lateralis: cloning, isoforms, and tissue expression. Gen. Comp. Endocrinol. 154:174-183.
Medler, S., T.R. Lilley, J.H. Riehl, E.P. Mulder, E.S. Chang and D.L. Mykles. 2007. Myofibrillar gene expression in differentiating lobster claw muscles. J. Exp. Zool. 307A:281-295.
Lee, K.J., H.-W Kim, A.M. Gomez, E.S. Chang, J.A. Covi and D.L. Mykles. 2007. Molt-inhibiting hormone from the tropical land crab, Gecarcinus lateralis: cloning, tissue expression, and expression of biologically active recombinant peptide in yeast. Gen. Comp. Endocrinol. 150:505-513.