Ontogeny of myosin heavy chain expression and prehensile
tail function in the gray short-tail opossum (Monodelphis domestica)
The link to a relevant background paper can be downloaded by clicking here.
I look forward to seeing all of you in seminar this week!!!!
A job well done by Dylan on his presentation. I believe he has proved beyond doubt that he is not just a party animal but a dedicated researcher.
ReplyDeleteSummary
Dylan’s work centers on the investigation of the differences in the expression of Myosin heavy chain (MHC) isoforms in the semi prehensile tail of a terrestrial opossum (Monodelphis domestica) as the opossum develops with age. These isoforms are MHC-1, MHC-2A, MHC-2X, and MHC-2B; with MHC-1 been the slowest but with more fibre and force and MHC-2B been the fastest but with less fibre and force. A mature opossum primarily uses his tail for nest building. It has been found that the more frequently a muscle is used; the likely hood there is a shift from the fast isoform of MHC to the slow isoform. These findings lead to hypotheses about developmental changes in MHC isoform content of the m. flexor caudae longus of opossum in relation to with tail use, specifically (i) juveniles should express fast developmental isoforms, in addition to having a large composition of fast MHC-2B throughout the tail, and (ii) at ages 3-5 months the developmental isoforms will transition into adult MHC-1 and 2A fibers, while MHC-2B will shift to the 2X isoform, each corresponding with the onset of nest construction behavior. To test these hypotheses, caudal muscle was harvested post-mortem from individuals ranging in age from 1–7 months, and MHC expression was quantified by RT-PCR, SDS-PAGE, and gel densitometry. To further evaluate how MHC isoform transitions correlate with nest construction, video data of tail use from individuals in different age groups (3 months to adulthood) was also collected and analysed for frequencies of tail behaviors. Preliminary data from protein gel analysis agrees with the hypothesis, indicating that there is a shift from a fast MHC isoform content in the juveniles to a slower composition in the adults.
Question
As Dylan mentioned, aside from hormones, what other factors do you think can enhance MHC isoform shift. Your answer does not need to be restricted to the m. flexor caudae longus or to the opossum.
As I'm sure Dylan explained, the main causes for shift in expression of myosin heavy chain isoform is developmental time and of use the muscles themselves. For example, there are two isoforms of MYH that are expressed early in development, MYH prei-natal and embryonic MYH. As the organism develops, the expression of these MYH gives way to the adult myosin heavy chain isoforms.
ReplyDeleteSubjecting people to high endurance training shifts myosin heavy chain isoform gene expression because a person will build more muscles expressing slow twitch myosin. In general, physical activity can alter myosin isoform expression.
ReplyDeleteI wouldn't be surprised if environmental factors had an effect on isoform expression. Certain synthetic molecules that are present in the environment (e.g. BPA) may also mimic hormones to cause the observed shifts in MHC expression.
ReplyDeleteDylan you did a great job on your presentation and explained everything very well!
ReplyDeleteAngiotensin Converting Enzyme (ACE) inhibition can affect muscle metabolic efficiency by altering the myosin content toward MHC isoforms.
Tardiff and colleagues suggest that thyroid hormone has the largest effect on the composition of MHC in the mammalian heart. This induces the α-MHC isoform.
ReplyDeletehttp://ajpheart.physiology.org/content/278/2/H412.long
It has been found that through the use of Functional Electronic Stimulation(FES) cycle training, over a period of 6 months, individuals with spinal cord injuries exhibited a marked increase in MHC type IIa and type I. However, there was a corresponding decrease in the type IIx MHC in the same patients.
ReplyDeleteIt has been found that the use of different pharmacological agents can be used to alter the expression of myosin heavy chain (MHC) isoforms within cardiac tissue by inducing different stresses upon the heart.
ReplyDeleteDylan’s presentation was a great glimpse into the sheer volume of work he has completed over the past two years. Good luck on the remainder of it!
ReplyDeleteVarious factors can produce these types of changes. Things such as heat shock proteins that respond to different stress conditions, natural developmental processes and strength and conditioning practices are all potential factors.
Dylan did a great job on his presentation! The amount of work he has done with his project and the level of data he has produced is amazing. I hope his work continues to produce just as good results.
ReplyDeleteA number of factors can influence these changes including congestive heart failure, various types of muscular training, and time of development.
Great Job Dylan!
ReplyDeleteTemperature seems to play a role in Cyprinus carpio (common carp) fast muscle isoform expression. At warmer water temperatures there is greater isoform expression.
Dylan did a great job on his presentation!
ReplyDeleteA number of various factors can enhance MHC isoforms. For example, calcium effect muscle contraction. Since calcium can hava an influence on contraction, it can intern have an effect on MHC isoforms.