NeuroPsychological Traits-Diversity: X-inactivation Mosaicisms
binstoct at ESSEX.HSC.COLORADO.EDU
Fri Jun 23 04:42:13 EST 1995
>>>On Thu, 22 Jun 1995, Richard Gordon wrote:
> The calico-cat effect should also lead to left/right hemispheric
> asymmetries exceeding those normally found.
> -Dick Gordon, U.Manitoba[Jun22,95]
1. The X-inactivation mosaicism would induce pleiotropic diversity of
neuropsychological traits only in cases of (i) mutated X-chromosome genes
affecting neuronal development and/or function (eg genes for MAO-A or for
FMR-1 re: fragile X syndrome, etc).
2. This kind of mosaicism occurs only in females, who have in each cell a
maternal-X and a paternal-X, only one of which is active in any given
cell (Lyonizatin hypothesis by Mary Lyon, 1961, and still supported by
data from numerous studies and not disproven).
3. The study by Happle (Arch Dermatol) cited in my original posting
shows an example of total left/right mosaicism, which Happle calls
a. This "rare" left/right mosaicisim might induce opposite
asymmetry effects in different individuals depending upon what side (L or
R) had the mutated gene as active.
b. Even in some cases of monozygotic twin females, one twin might have a
left sided activation of the mutation and the other twin might have a right
sided activation of the mutation.
4. Far more frequently, the "calico-cat" effect would not be arranged in
left/right separation. According to visually observable patterns of
X-linked mosaicisms of human skin (eg as illustrated in the Rudolf Happle
study), various "calico cat" patterns are possible. According to the Tan
et al study (Development 121.1029-39 1995) the in-brain mosaicisms are
three dimensional and complexly "calico-esque".
5. Consider the case of 200 females tested for left/right hemispheric
effects and consider that of the 200, one hundred have normal
X-chromosomes and one hundred have mutations of the same X-chromosome
gene affecting cognition, emotion, and behavior (ie aspects of CNS
a. The data from normal X-chromosomes females would show fairly
traditional curves re left/right hemispheric effects.
b. The data from females with either a maternally or paternally inherited
X-chromosome mutation of a gene affecting CNS function would be more
diversely and complexly patterned.
6. I can't help but think that some such mutated X-gene individuals would
show increased left-like tendencies, some just the opposite, and most
subjects would present blurrings of traditional left/right distinctions
for any given trait.
*** *** *** *** ***
How X-linked mosaicisims would affect left/right asymmetry and related
scores on cognitive and/or emotional measures is quite challenging.
You've raised a good point. Further input re: "mosaicisms meet L/R
asymmetries" will be important to understanding both the mosaicisms and
Thank you for the reply...
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