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 Post subject: X-Factor - Large Heart
PostPosted: Mon Aug 24, 2015 9:05 am 
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Here is a new paper on the genetics behind cardiovascular capacity and cardiac remodelling.

Aerobic exercise training promotes physiological cardiac remodeling involving a set of microRNAs - http://ajpheart.physiology.org/content/309/4/H543.abstract

microRNA's are a small non-coding RNA molecule that operates/alters gene expression. The four cardiac specific MicroRNA's

miRNA-1 - located on Chromosome 8 (http://www.mirbase.org/cgi-bin/mirna_entry.pl?acc=MI0012746)
miRNA-133a - located on Chromosome 8
miRNA-133b - located on Chromosome 20
miRNA-208a - located on Chromosome 1
miRNA-208b - located on Chromosome 1
miRNA-499 - located on Chromosome 22
miRNA-143 - located on Chromosome 14
miRNA-27a - located on Chromosome 7
miRNA-27b - located on Chromosome 23
miRNA-29a - located on Chromosome 4
miRNA-29b - located on Chromosome 4

Nothing located on the X....

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PostPosted: Sat Sep 12, 2015 9:00 am 
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Brogers

In a study called the Potential Role of Maternal Lineage in Breeders Strategy there is evidence that the dam is more influential than the sire in generating elite runners. They hypothesize that mt DNA may cause this difference. Although mt DNA plays a role in the above success in generating elite runners, the X chromosome may also be an important part of the above elite runners prowess.

Example- The great mare,Plucky Liege produced 6 stakes winning sons and 4 of them topped the broodmare sire lists-Sir Gallahad, Bull Dog, Bois Roissell, and Admiral Drake. Plucky Liege had two superior X chromosomes and mothered 4 sons whose daughters got one of these great Xs and transmitted it to 50 percent of their offspring. Variants on the X chromosome that relate to elite performance play an important role in Plucky Liege's vast influence on the breed.


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PostPosted: Mon Sep 14, 2015 6:19 am 
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Stan

Your statement that Plucky Liege passed one of her two X chromosomes on to her sons is incorrect. During meiosis each egg produced by any filly or mare contains a recombined X chromosome that contains parts from each of her two X chromosomes and not one of the X chromosomes she received from her sire or dam. Furthermore, because of the recombination each egg produced contains an X chromosome unique to that egg, meaning that each of the 4 stallions cited by you contain a different recombined X chromosome. What each of these champion broodmare sires did receive was the same mtDNA.

In addition, genetic science has documented that the X chromosome contains a limited amount of performance related variants.

DDT


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PostPosted: Tue Sep 15, 2015 1:08 pm 
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stancaris wrote:
Brogers

In a study called the Potential Role of Maternal Lineage in Breeders Strategy there is evidence that the dam is more influential than the sire in generating elite runners. They hypothesize that mt DNA may cause this difference. Although mt DNA plays a role in the above success in generating elite runners, the X chromosome may also be an important part of the above elite runners prowess.


I've read the paper. It was done by Allan Davie's group out of Australia. Theyve done a lot of work on mtDNA so this was a paper whose purpose was to tie mtDNA to performance.

What they failed to explain in the paper is that because of selection, there is less variance in performance coming from the sire. That is, because the bar to be a stallion is so high, the difference in terms of performance between sires is low. Conversely, because the bar to be a broodmare is quite low (that is, anything with ovaries can get bred), the variance of performance is much higher in mares. Thus, it becomes a self fulfilling prophecy. The more we select on sires, and make the bar to become a stallion high, the less we select on mares, and therefore the variance in offsprings performance revolves more around the quality of the mare, not the sire.

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PostPosted: Tue Sep 15, 2015 2:41 pm 
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Brogers stated: "therefore the variance in offsprings performance revolves more around the quality of the mare, not the sire."

I agree with the above statement but what about a mare's X chromosome as an important contributor to that performance? A son receives more nuclear DNA from his dam because the X chromosome carries more genes than does the much smaller y chromosome. Plucky Liege transmitted one of her X chromosomes to 6 of her sons that became stakes winners and 4 of these sons led the broodmare sire list multiple times.
(Sir Gallahad, Bull Dog, Bois Rousell, and Admiral Drake). These great broodmare sire sons transmitted a powerful X chromosome (which came from Plucky Liege) to every one of their daughters and they in turn transmitted around 50% of Plucky Liege's X chromosome to their progeny which were big earners on the track.

Sex Linked inheritance patterns support the above view that the X chromosome plays an important role in broodmare sire success because a broodmare sire transmits his X to all his daughters and none of his sons. Sir Gallahad led the North American broodmare sire list 12 times. No other broodmare sire since 1924 led the list that many times. It seems likely that his X was important in that success.


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PostPosted: Tue Sep 15, 2015 6:37 pm 
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The variants provided by the 31 autosomes also passed on by the mare, female imprinted genes, the autosomes contributed by the covering sire, the overall quality of the mares, the total number of foals running during any given year, the total number of mares represented in any given year and environmental aspects are the primary factors in broodmare sire success. The contribution of the genes carried on the X chromosome, confirmed by genetic science, has very little to do with elite performance, and therefore should not be considered as a primary factor for broodmare sire success.

DDT


Last edited by DDT on Tue Sep 15, 2015 9:32 pm, edited 1 time in total.

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PostPosted: Tue Sep 15, 2015 7:39 pm 
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Stancaris,

You've cherry picked my statement to suit your needs. The pre-amble to the 'therefore' states the reason for the statement.

I think about a year or so ago I said that there are some X-Chromosome variants that have some relationship to performance but that other SNPs on other chromosomes have far greater effect and are more important than the X Chromosome ones when it comes to performance.

Leave the X-Factor alone....you are beating a dead horse.

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PostPosted: Wed Sep 16, 2015 3:17 pm 
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Brogers: Sir Gallahad led the broodmare sire list in North America 12 times but according to you his X chromosome had little to do with that success.

How about the fundamental pattern of heredity whereby a broodmare sire transmits his X chromosome (almost entirely intact) to all his daughters and none of his sons. All maternal grandsons of Sir Gallahad receive around 50% of the genes that were carried on his X chromosome. Since they have nothing on their y chromosome to suppress those genes each one of those DNA codes will be expressed.

You said last year that there are variants on the X chromosome that relate to elite performance and that one of them reached statistical significance. That is real data from genomic research to make me say that the X chromosome is important to broodmare sire success.


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PostPosted: Thu Sep 17, 2015 8:27 am 
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To equate broodmare sire success with the leading broodmare sire list by progeny earnings, or for that matter, any list controlled by progeny earnings we should consider the fact that one or two superior performers may be the reason for the stallions appearance on the lists. Stating that the number of times a broodmare stallion or stallion appears on the lists is related to or the result of genes carried on the X chromosome overlooks the fact that one or two superior runners can and often do skew the standings As an example of this just look at the year 2004, Elusive Quality was the leading sire purely because of the earnings of Smarty Jones. Smile, the broodmare sire of Smarty Jones made it to number 9 on the leading broodmare sires list for his one and only appearance on the list. Numbers, opportunity and environmental factors are and always will be the primary factors at work and not genes carried on the X chromosome.

DDT


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PostPosted: Sat Sep 19, 2015 4:18 pm 
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stancaris wrote:
[brogers] said last year that there are variants on the X chromosome that relate to elite performance and that one of them reached statistical significance. That is real data from genomic research to make me say that the X chromosome is important to broodmare sire success.

Kudos for giving at least one source advance notice that you'll be mis-representing their remarks.

Your presupposition that x variants are more important to elite performance, therefore to broodmare sire success, than is actually the case has no obvious credible basis. It probably derives from Haun's "X factor" hypothesis, central to which was the idea that heart size is controlled on the x chromosome. Genome-based evidence indicates that's wrong but, without offering evidence for any specific x variants relevant to other aspects of TB performance or, really, even manifesting any evidence of a thorough grasp of basic genetics, you continue to aggrandize the importance of the x. Even Haun never quite went so far as to represent the "X factor" as a major predictor of elite performance - except maybe in elite performers. If you can wrap your mind around that you ought to recognize that it's roughly consistent with the x being of some minor importance to elite performance.

Last year you said you were "in discussions with a person doing genomic research on thoroughbreds". How did those "experiments" turn out? Or are you still "not at liberty to divulge the results"?


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PostPosted: Fri Dec 30, 2016 10:33 pm 
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Here is a link to a Thesis completed by an Australian researcher looking at the nuclear SNPs that are in genes associated with cardiac hypertrophy (large heart).

Its the start of putting a genetic basis on cardio size and its noteworthy that none of the SNPs are on the X Chromsome.

http://espace.library.uq.edu.au/view/UQ:388431

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PostPosted: Sun Jan 01, 2017 4:58 pm 
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Looks like a fascinating article, which unfortunately, is beyond my comprehension in terms of an understanding of the genetics underneath it, Still, it's pointing to tests that can tell whether the large heart is indicated, which could be huge. I guess the large heart obviously has the possibility of relationship to performance, but I'm wondering if studies are out there that identify to what degree of significance (i.e. what percent of total population has large heart, and what percentage of those were elite performers, and what percentage were not (and why not - environment, training, other genetics)?

Also of interest was this quote, "within this population may suggest that current breeding strategies are not maintaining the genetic health of the population." which may speak to the proverbial question of whether the TB population is being bred into mediocrity and whether the previous generations were, indeed, genetically superior and would run the heels off of today's nags?

jm

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PostPosted: Wed Jan 18, 2017 1:30 am 
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There is always some new scientific research coming out telling us that zero calorie diet soft drinks with artificial sweetners actually lead to weight gain rather than weight loss, that somehow the zero calorie artificial sweeteners are tricking the body into packing on addititional weight. I'm always baffled that the masses use these supposed scientific studies to vilify aspartame and artificial zero calorie sweeteners. It's absolutely an outrageous crock of b.s. If artificial zero calorie sweeteners were making people get fat, then we could ship zero calorie artificial sweeteners all over the 3rd world and put an end to starvation and skinny scrawny little kids dying of hunger and lack of fat on their bodies.

So throw your studies out there, this does this and that does that. B.s. studies a dime a dozen and most just as worthless as an aspartame study supposing that zero calorie soft drinks make people fat.

Any thoroughbred breeder knows that some stallions make great broodmare sires, we know Buckpasser in the pedigree has proven to be helpful, so fire away with the scientific study b.s.


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PostPosted: Wed Jan 18, 2017 12:36 pm 
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The only thing that's fashionable in the industry outside of Tapit, War Front and one or two others is an unproven sire regardless of their heart size. I don't see that ever changing so even if they can say "breed to this horse and we guarantee you will get it" that isn't going to change the mindset. Perhaps if that can lead to something meaningful like how to fix forward/back/offset that would make a big difference.

Imagine how much better a sire Tapit could be if he weren't passing along his knees because no matter how large a heart they have it cannot possibly overcome that trait because sooner or later, the way they put down their feet, is going to catch up with them.


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PostPosted: Wed Jan 18, 2017 4:53 pm 
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Jeff wrote: "... so fire away with the scientific study b.s."

OK. From The Horse/1/18/17: "Scientists Find Genes Behind Crooked Legs in Shetland Ponies"
A hereditary disease--skeletal atavism--leads to disturbed skeletal development and usually requires euthanasia. Read Now

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