Synapses, Synesthesia, & Genes
A recent study about Fragile X---the most common inherited form of mental retardation and single gene cause of autism---published in the February 4th Journal of Neuroscience is about presynaptic function in Fragile X; on what happens on the "sending side" of the synapse, when information from one neuron flows to another one. The study specifically discusses how a presynaptic Fragile X granule is expressed in the developing brain; as the authors note in the abstract:
These findings suggest that Fragile X proteins play a distinct, presynaptic role during discrete developmental epochs in defined circuits of the mammalian CNS [central nervous system]. We propose that the neurological defects in Fragile X syndrome, including the autistic features, could be due in part to the loss of FMRP function in presynaptic compartments.
In an interview, Justin Fallon, professor of neuroscience at Brown University says that "'The implication is that pre-synaptic defects could contribute to the pathology in autism in Fragile X.'" A 2007 Science article indeed suggested that autism's cause may "reside in abnormalities at the synapse." Some media sources are referring to this study as potentially leading to a "new autism treatment" in the form of drug treatments, although it's only in about of 2% to 6% of children diagnosed with autism that the Fragile X gene mutation is the cause, according to the National Fragile X Foundation.
My son tested negative for Fragile X; the media ought to be clearer in noting that the Fragile X gene mutation accounts for a small percentage of autism cases. Research that looks at synaptic functioning and autism has been of interest to me in and of itself. Reflecting not only on what my son struggles to learn---anything involving language, written and spoken---but how he struggles----it often seems to require so much time and effort for him to process sensory stimuli---makes findings about synapses particularly of interest. There's things about Charlie (how he holds and moves his body; his need for deep pressure of a massage-like sort) that I started to first notice when I was expecting him: Charlie has always been Charlie.
Even more, he's some thorough combination of Jim and me, of what he inherited from us.
Another recently published study in the February 5th American Journal of Human Genetics seeks to identify the genes for synesthesia. Dr. Julian E. Asher of the Department of Genomic Medicine at Imperial College London is the lead researcher; from a press release:
The research team identified four candidate regions linked with susceptibility to synaesthesia but no support was found for an earlier theory of linkage to the X-chromosome. Although the resolution of the scan makes identifying candidate genes challenging, the researchers identified a number of interesting genes.
"The region on chromosome 2 with the strongest linkage is particularly interesting as it has been previously linked to autism," offers Dr. Asher. "Sensory and perceptual abnormalities are common in autism spectrum conditions and synaesthesia is sometimes reported as a symptom." Candidate genes associated with epilepsy, dyslexia, learning and memory are also located in the candidate regions.
The findings indicate that the genetic basis of auditory-visual synaesthesia is more complex than originally believed and may be due to a combination of multiple genes subject to multiple modes of inheritance. "This study comprises a significant step towards identifying the genetic substrates underlying synaesthesia, with important implications for our understanding of the role of genes in human cognition and perception," concludes Dr. Asher.
"A combination of multiple genes subject to multiple modes of inheritance": There's not some "autism gene" that (in an oversimplified understanding of genes) is passed on from parent to child. A suggestion for a unified genetic theory of autism considers the role of spontaneous mutations in causing autism; such de novo mutations may account for up to 30 percent of cases of autism.
A bit back I wrote about there being a little autism in all of us. There's a clear combining of Jim and me in Charlie, who looks exactly like me, with the same tall, lanky frame as his dad. Also like his dad, Charlie loves to be in motion (trains and cars and walking and running and biking) and has bouts of hyperness and lulls of quietude. Like me, he can have incredibly obsessive focus accompanied by a need for order, and then there's that synesthesia business. However Charlie came to be, the resemblances are uncanny.
Truly, he's one of us, and we're sticking with him.
COMMENTS (4)