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#Post#: 68912--------------------------------------------------
More wolves-- "little dog gene" existed in wolves
before dog domestication
DIR By: guest114
Date: January 31, 2022, 7:45 pm
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HTML https://www.sciencedaily.com/releases/2022/01/220127114340.htm
The paper is here:
HTML https://www.cell.com/current-biology/fulltext/S0960-9822(21)01723-1<br
/>
First off, let me clarify some points that are confused in the
sciencedaily article:
"..when the team looked at the DNA of a 54,000-year-old Siberian
wolf (Canis lupus campestris) they found that it, too, possessed
the growth hormone mutation. "
1) IGF-1 (insulin-like growth factor 1, aka somatomedin C) is
not Growth Hormone (GF)-- it is stimulated by growth hormone.
For instance, in humans Laron syndrome causes low IGF-1 because
of growth hormone receptor defects.
There's no known IGF-1 mutation that is linked to dwarfism in
humans, probably because low or no IGF-1 tends to cause severe
low blood sugar. Knock-out mice models out show neurological
defects and prenatal lethality.
So, a viable IGF-1 polymorphism is not likely to be a mutation
affecting its function, but something in how it is turned on.
This is why they got somewhere AFTER : "Jocelyn Plassais
(@JocelynPlassais), a postdoc in geneticist Elaine Ostrander's
lab, suggested that they search for sequences around the gene
that were positioned backwards and confirm if any were present
in other canids and ancient DNA."
They were looking for inverted sequences around genes
indicating inactivated or mutated promoters. Sometimes bits of
chromosomes can get switched around (chromosomal inversions)
because of very similar sequences at both ends. Same for genes
with lots of similar promoter sequences on both ends.
"With this approach, their team found a reverse form of the
insulin-like growth factor 1 (IGF1) gene with variants that
correlated to dog body size." That's the biggie. It held up
through analysis. The IGF-1 gene was identified in small dogs
over a decade ago, but establishing whether this existed in
wolves took time. They identified this gene in Arabian wolves,
which are quite small BUT also have dog admixture, so it was not
clear if this was from dogs OR what.
"Or what" seems to have been proved-- it well predates all
dogs. It's the big dog variant that is new. The actual Cell
Article explains.
This fits my suspicion we originally tamed a smaller wolf
variant to dogs in the first place; Japanese wolves (which are
descended from ancient Siberian wolves) was very small indeed,
if bigger than Arabian wolves.
HTML https://en.wikipedia.org/wiki/Japanese_wolf
indeed, most dogs
have a small trace of Japanese wolf after a post-domestication
admixture into Japanese dog breeds.
NOW to wolves.
The Steppenwolf (that's the subspecies listed-- the Caspian
wolf) is smaller than the Eurasian wolf, being around 74-88 lbs
on average vs 85-110 lbs. So that's significantly smaller, but
not tiny. I'm not clear if they were smaller 54,000 years ago
or not. This specimen could be related to the ancestral pool
leading to Japanese wolves.
This is a nice find, proving this ancient DNA research proves
the gene existed in wolves well before dogs were domesticated
and probably was widespread at low frequencies, and then
collapsed and went rare as wolf populations plummeted after the
Pleistocene. It also gives one possible marker to look for in
ancient wolf DNA too when looking for the ancestor of dogs.
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