✍ Scribed by Kubota, Takeo; Oga, Satoko; Ohashi, Hirofumi; Iwamoto, Yasuhiko; Fukushima, Yoshimitsu
No coin nor oath required. For personal study only.
Bo ¨rjeson-Forssman-Lehmann (BFL) syndrome is an X-linked recessive disorder characterized by minor facial anomalies, obesity, epilepsy, and severe mental retardation. The phenotype of male patients is usually severe, whereas that of carriers is less severe, suggesting X-linked incompletely recessive inheritance. A recent linkage study mapped the BFL syndrome gene to Xq26-q27. The etiology of the condition in female patients with full manifestations is not known, although nonrandom Xchromosome inactivation has been considered. We recently developed an assay for Xinactivation studies based on the methylation-specific polymerase chain reaction (PCR) technique. Using the methylationspecific PCR assay, a woman with typical findings of this syndrome was shown to have an extremely skewed X-inactivation pattern. This finding suggests that the full manifestations of the BFL syndrome in carriers may be caused by skewed X inactivation with a high proportion of cells in which the X chromosome with a normal gene be inactivated, leaving the X chromosome with a mutant gene active. Am.
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X inactivation is the process by which mammalian females achieve dosage compensation by transcriptionally silencing one X chromosome. In chromosomally normal females, this process is random. However, most females with one abnormal X chromosome demonstrate complete skewing of X inactivation, presumab