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TTR (transthyretin)

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Human Uniqueness Compared to "Great Apes": 
Likely Difference
MOCA Domain: 
Genetics
MOCA Topic Authors: 
Ajit Varki

Transthyretin (TTR) is a protein made in the liver and the choroid plexus of the brain, resulting in its presence in the blood plasma and cerebrospinal blood respectively. It the principal thyroid hormone transport protein in cerebrospinal fluid and is responsible for delivering the hormone to the brain. Expression levels in humans compared with "great apes" appear to be increased both in circulating blood and in cerebrospinal blood, and this is presumed to be due to increased gene expression at the sites of synthesis mentioned. There may be some connection to apparent differences in thyroid hormone metabolism between humans and chimpanzees. The biological significance of this event is unknown. One comparative study between humans and chimpanzees suggested that TTR has has undergone recent positive selection in humans. Notably transthyretin is also the carrier for retinol binding protein, which keeps retinol in the circulation.

Type of Human-Specific Changes in TTR
Tissue Expression Pattern Change

 

Genetics Topic Attributes

Gene symbols follow the HUGO Gene Nomenclature Committee standard.

Gene Symbol:
TTR (TTR: transthyretin)
Type of Human-Specific Changes:
Expression Pattern Change
Related MOCA Topics
Related Topics:
TitleCertainty
Brain SizeNone
Thyroid Hormone Metabolism None
Referenced By:
TitleCertainty
Thyroid Hormone Metabolism Likely
Timing

Timing of Appearance of the Difference in the Hominin Lineage.

For this entry assume that

  • the common ancestor of humans and old world monkeys was 25000 thousand (25 million) years ago
  • the common ancestor of humans and chimpanzees was 6000 thousand (6 million) years ago
  • the emergence of the genus Homo was 2000 thousand (2 million) years ago
  • the common ancestor of modern humans was 100 thousand years ago

 

Definite Appearance: 
100 Thousand Years
References: 

Gagneux, P., Amess, B., Diaz, S., Moore, S., Patel, T., Dillmann, W., Parekh, R., and Varki, A. 2001. Proteomic comparison of human and great ape blood plasma reveals conserved glycosylation and differences in thyroid hormone metabolism. Am J Phys Anthropol. 115:99-109.
 
Nadezhdin EV, Vinogradova TV, Sverdlov ED. 2001 Interspecies subtractive hybridization of cDNA from human and chimpanzee brains.Dokl Biochem Biophys Nov-Dec;381:415-8.