Anomiel wrote:
Perspective on neurodiversity. In the course of their recent analysis of the Denisovan DNA, Meyer and Pääbo identified 23 highly conserved areas of the human genome that seem to be unique to our kind. Eight of those contain genes that previous studies have tied to nerve growth and other aspects of brain function. And three of the conserved genes — ADSL, CBTNAP2, and CNTNAP2 — have been implicated in some forms of autism.
The author of that piece appears to have failed to understand what the paper itself actually claimed. As far as I can figure out, it does not claim that we got those genes from the Denisovans. The study itself appears to be off-limits to those of us without the right access, but we can find some clues to what it said from people with a much stronger background than the author of the above quote.
From an anthropologist who studies the bones and genes of ancient humans and who is Associate Professor of Anthropology at the University of Wisconsin—Madison. He is also Associate Chair of Anthropology, at Howard Hughes Medical Institute (HHMI) Faculty Fellow, and an associate member of both the Department of Zoology and the J. F. Crow Institute for the Study of Evolution.:
With my foremost interests being in neuroscience and genetics, what I found to be most fascinating is what the Denisovan girl has taught us about the evolution of the human brain. At least eight genes associated with nerve growth (including SLITRK1, KATNA1, ARHGAP32 and HTR2B) have emerged since the time of the Denisovans. Other conserved genes associated with language development (ADSL, CBTNAP2 and CNTNAP2) were present but have undergone changes within modern-day humans. These genes are thought to be among the causes of autism if they mutate, which also suggests that there may be a link to the emergence of empathy within humans. The appearance and alterations of these genes demonstrates how far our complex cognitive processes have come since the time of our ancestors.
Further down, he quotes Meyer:
Quote:
One way to identify changes that may have functional consequences is to focus on sites that are highly conserved among primates and that have changed on the modern human lineage after separation from Denisovan ancestors. We note that among the 23 most conserved positions affected by amino acid changes (primate conservation score ≥ 0.95), eight affect genes that are associated with brain function or nervous system development (NOVA1, SLITRK1, KATNA1, LUZP1, ARHGAP32, ADSL, HTR2B, CBTNAP2). Four of these are involved in axonal and dendritic growth (SLITRK1, KATNA1) and synaptic transmission (ARHGAP32, HTR2B) and two have been implicated in autism (ADSL, CNTNAP2). CNTNAP2 is also associated with susceptibility to language disorders (27) and is particularly noteworthy as it is one of the few genes known to be regulated by FOXP2, a transcription factor involved in language and speech development as well as synaptic plasticity (28). It is thus tempting to speculate that crucial aspects of synaptic transmission may have changed in modern humans.
And this seems to be from someone else involved in the study:
The earlier genomes (1,2) allowed to identify less than half of all derived genomic features that became fixed or nearly fixed in modern humans after their divergence while the current Denisova genome provides an essentially complete catalogue. In 111,812 single nucleotide changes and 9,499 insertions and deletions, we identified 260 human‐specific SNCs that cause fixed amino acid substitutions in well‐defined human genes, 72 fixed SNCs affecting splice sites, and 35 SNCs affecting well‐defined motifs inside regulatory regions. We note that among the 23 most conserved positions affected by amino acid changes, eight affect genes associated with brain function or nervous system development (NOVA1, SLITRK1, KATNA1, LUZP1, ARHGAP32, ADSL, HTR2B, CBTNAP2). Four of these are involved in axonal and dendritic growth (SLITRK1, KATNA1) and synaptic transmission (ARHGAP32, HTR2B) and two have been implicated in autism (ADSL, CBTNAP2).
SNC = "Single Nucleotide Change"
There are some apparent discrepancies between them. One author says that the eight genes emerged since then while another says there are SNCs affecting the sites of the genes since the Denisovans.
Also of interest are some supplementary notes. In
http://genetics.med.harvard.edu/reich/Reich_Lab/Publications_files/Meyer_Science_Supp_DenisovaSeq.pdf. It's 132 pages long and will take a while to read so I'll save that for later.
So am I missing something? Where does it say that we inherited those genes from the Denisovans? And for the two or three related to Autism, that relation to Autism seems to exist in mutations of the genes, not the genes themselves.
14 Jan 2013, 1:11 am
