Friday, May 7, 2010

Neanderthal genes?!?

Many months ago I read what I considered to be kind of a weird essay I found on the web in which the author argued that many traits we consider to be autistic are, in actuality, remnants of Neanderthal genes. He (or she?) argued that Neanderthals had interbred with humans, and that this accounted for certain differences in some individuals. I dismissed it as pretty far-fetched.

Until this morning, that is -- when I read this Washington Post article that in fact researchers have apparently proven that Non-African humans did in fact interbreed with Neanderthals, and that except for those of us with African ancestry, between 1 and 4% of our genes can be traced to the Neanderthals.

And -- at least one of those genes -- CADPS2 -- has been linked to autism. Here's what my less than exhaustive search turned up about CADPS2 (from this article):

CADPS2 (also called CAPS2) encodes a protein that regulates the trafficking and release, or exocytosis, of vesicles containing cargo such as neurotrophic factors, which influence brain cell maturation and survival. To determine whether the absence of CADPS2 influences autism development, the researchers generated mice carrying a disrupted version of CADPS2.

The mutant mice exhibited normal visual, auditory, olfactory and motor function, all of which are normal in autistic patients. [EDITOR'S NOTE: I am astonished to read this. In my experience, most autistic children are impaired in at least some of these functions. I don't see how this is consistent with the sensory processing component of autism. Surely most of us have experience these issues in our children?] However, like autistic humans, CADPS2-deficient mice engaged in fewer social interactions with other mice, displayed heightened anxiety and reduced exploration in unfamiliar environments, and were hyperactive even in familiar surroundings.

Absence of CADPS2 resulted in cellular defects mirroring those frequently observed in the brains of autistic patients, such as reduced development and impaired survival of certain varieties of brain cells including some GABAergic interneurons and cerebellar Purkinje cells. Provision of brain-derived neurotrophic factor (BDNF), a protein found in CADPS2-associated vesicles in normal mice, rectified these cellular abnormalities.

I don't know what that means, but I guess it's time for me to learn to be a little more open-minded.

1 comment:

  1. Autism: The Eusocial Hominid Hypothesis


    ASDs (autism spectrum disorders) are hypothesized as one of many adaptive human cognitive variations that have been maintained in modern populations via multiple genetic and epigenetic mechanisms. Introgression from "archaic" hominids (adapted for less demanding social environments) is conjectured as the source of initial intraspecific heterogeneity because strict inclusive fitness does not adequately model the evolution of distinct, copy-number sensitive phenotypes within a freely reproducing population.

    Evidence is given of divergent encephalization and brain organization in the Neanderthal (including a ~1520 cc cranial capacity, larger than that of modern humans) to explain the origin of the autism subgroup characterized by abnormal brain growth.

    Autism and immune dysfunction are frequently comorbid. This supports an admixture model in light of the recent discovery that MHC alleles (genes linked to immune function, mate selection, neuronal "pruning," etc.) found in most modern human populations come from "archaic" hominids.

    Mitochondrial dysfunction, differential fetal androgen exposure, lung abnormalities, and hypomethylation/CNV due to hybridization are also presented as evidence.