The MYH16 gene encodes a protein called
myosin
Myosins () are a Protein family, family of motor proteins (though most often protein complexes) best known for their roles in muscle contraction and in a wide range of other motility processes in eukaryotes. They are adenosine triphosphate, ATP- ...
heavy chain 16, which is a muscle protein in mammals. At least in primates, it is a specialized muscle protein found only in the
temporalis
In anatomy, the temporalis muscle, also known as the temporal muscle, is one of the muscles of mastication (chewing). It is a broad, fan-shaped convergent muscle on each side of the head that fills the temporal fossa, superior to the zygomatic ...
and
masseter
In anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it is the ...
muscles of the jaw.
Myosin heavy chain proteins are important in
muscle
Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...
contraction, and if they are missing, the muscles will be smaller.
In non-human primates, MYH16 is functional and the animals have powerful jaw muscles. In humans, the MYH16 gene has a
mutation
In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, ...
that causes the protein not to function.
Although the exact importance of this change in accounting for differences between humans and other
ape
Apes (collectively Hominoidea ) are a superfamily of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and Europe in prehistory, and counting humans are found global ...
s is not yet clear, such a change may be related to increased
brain size
The size of the brain is a frequent topic of study within the fields of anatomy, biological anthropology, animal science and evolution. Measuring brain size and cranial capacity is relevant both to humans and other animals, and can be done by wei ...
and finer control of the jaw, which facilitates speech.
It is not clear how the MYH16 mutation relates to other changes to the jaw and skull in early human evolution (for example, whether the MYH16 mutation happened first and led to other changes, or whether the MYH16 mutation happened after other changes made the MYH16 protein no longer necessary).
The initial discovery of the human MYH16 mutation was published in 2004 by a team at the
University of Pennsylvania
The University of Pennsylvania (Penn or UPenn) is a Private university, private Ivy League research university in Philadelphia, Pennsylvania, United States. One of nine colonial colleges, it was chartered in 1755 through the efforts of f ...
led by
Hansell H. Stedman.
The date of the mutation has variously been estimated at 2.4 million years ago
or 5.3 million years ago.
The MYH16 gene is present in
dog
The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the gray wolf. Also called the domestic dog, it was selectively bred from a population of wolves during the Late Pleistocene by hunter-gatherers. ...
s,
but does not appear to be present in
mice
A mouse (: mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...
.
References
External links
Story from Science Scoop*
*
{{Cytoskeletal Proteins
Mammal genes