Wednesday, January 28, 2004

Untrustworthy Reporting on Genetics

I happened to come across an article on Yahoo containing claims that, if true, would be sensational. Supposedly, a premutation expansion of the Fragile-X Mental Retardation 1 (FMR1) gene, associated in male carriers with several debilitating syndroms in later life, is also associated with higher intelligence in early to mid-life; if this statement is true, it would be revolutionary for two reasons:

  1. it would represent the first gene of which we are aware to have been definitively linked to higher intelligence
  2. it would provide an instance of a human gene providing a benefit during the reproductive years at the cost of lower functioning once those years were past. This mechanism has long been suspected as being implicated in the aging process - why code for immortality at the expense of present reproductive fitness, especially if life expectancy is already limited by predation and other hardships?
Needless to say, however, I am extremely sceptical, not least because of the source of this information.
TUESDAY, Jan. 27 (HealthDayNews) -- Doctors may frequently be confusing Parkinson's disease, Alzheimer's and similar age-related neurological ailments with the symptoms of a recently discovered genetic disorder that's surprisingly common yet unfamiliar to most physicians.

The illness is called fragile X-associated tremor/ataxia syndrome, or FXTAS (pronounced fax-tass). It typically affects men over age 50, causing tremors, balance problems and dementia, which all progressively worsen over time, much like Parkinson's and related conditions. People afflicted by the genetic flaw appear normal through childhood and much of their adult life.

FXTAS is closely related to fragile X syndrome, the leading cause of inherited mental retardation.

Fragile X occurs when cells in the body don't product a protein produced by the fragile X mental retardation 1 gene (FMR1). Men with fragile X syndrome suffer from mental and motor impairment, autism, elongated faces, enlarged ears and testes, and connective tissue problems. In women, retardation may be accompanied by premature menopause in about 25 percent of people.

Previous studies have found that about one in 259 women and one in 813 men in the United States are born with oversized versions of FMR1. The gene is bulged by stretches of repeating DNA, called "premutation expansions," whhich cause cells to think they're not producing enough FMR1.

Rather than cause retardation, this error often leads to high intelligence and achievement, at least in early and mid-life, says Dr. Randi Hagerman, a fragile X expert at the University of California at Davis and a co-author of the study.

"Generally, these individuals are very smart and very productive," Hagerman says. But starting in their 50s and beyond, she adds, they begin to show signs of brain damage -- the result, apparently, of tiny pearl-like protein clusters that accumulate in their neurons.

Rather than take it for granted that HealthDayNews had gotten Dr. Hagerman's words right, I decided to track down the abstract for the actual article, which can be found here. I'm not a JAMA subscriber, so I can't tell what's in the full article, but nothing in the abstract I saw indicated that this gene had anything to do with "high intelligence." The OMIM entry for FMR1 also failed to mention anything about above-normal intelligence, while the PubMed entry for an earlier Am. J. Hum. Gen. article by the same team was similarly uninformative. Now, given as sensational a claim as the one put forward in this article on Yahoo, how likely is that none of the informed sources would have said anything about it?

The full JAMA article will be freely available to the general public in 6 months, but I'm doubtful that the claim that this premutation expansion "often" confers "high intelligence" will be substantiated. At best, I'm sure, it will be revealed that the gene had no appreciable negative impact in early to mid-life, a much weaker claim; nevertheless, a new myth of a putative "intelligence gene" will probably have been born. Such are the fruits of shoddy science reporting.