The fragile X: a scanning electron microscope study.

Abstract

SUMMARY Scanning electron microscopy (SEM) has been used to study the fragile X chromosome.The fragile site appears as an isochromatid gap in the majority of cases, confirming light microscope (LM) observations. SEM has allowed a more precise location of the fragile site to the Xq27-3 region.Light microscope (LM) studies have indicated that the fragile site on the X chromosome is most frequently observed as a non-staining gap of variable width, usually involving both chromatids. However, there is some uncertainty as to the exact position of this site. Sutherland1 2 defined it to be either in the Xq27 or Xq28 region. The enhanced resolution provided by scanning electron microscopy (SEM) has allowed both confirmation of the morphology and precise location of the fragile site by application of a technique used previously to karyotype human metaphases by SEM.3 Materials and methodsHeparinised peripheral blood, from a male patient known to have a fragile X chromosome, was cultured in TC 199 medium with Earle's Salts without serum supplementation and containing phytohaemagglutinin for 66 hours at 37°C. A total of 0 01 ,ug/ml colcemid was added for 1 hours. Cells were incubated in 75 mmol/l KCI for 5 minutes at room temperature followed by three washes in methanol-acetic acid fixative (3:1). Between the second and third washes cells were incubated for I hour at -20°C. Chromosomie spreads were made by dropping suspension onto coverslips, followed by air-drying. Several coverslips were stained in 20% Giemsa in Gurr's buffer (pH 6.8) for 8 minutes at room temperature for LM analysis.Two to three days later the remaining coverslips were G banded using a method modified from the technique of Seabright4 as follows: coverslips were incubated in 0.025% trypsin in 0.8504 saline for

Determination of a translocation chromosome by atomic force microscopy

“…The images of AFM are compatible with previous scanning electron microscopy studies (Harrison et al 1983).…”

Cytological mapping of the human glucose-6-phosphate dehydrogenase gene distal to the fragile-X site suggests a high rate of meiotic recombination across this site.

“…The precise location of the X-linked fragile site has now been established by prophase banding (22) and by electron microscopy (23) to be Xq27.3. Formal genetic analysis (Table 1) had previously shown close linkage of G6PD to hemophilia A (25), Deutan and Protan color blindness (12,28), and adrenal leukodystrophy (27).…”

Synaptic Dysfunction in Neurodevelopmental Disorders Associated with Autism and Intellectual Disabilities

“…Moreover, Lubs reported that the affected males had macroorchidism (large testes); large, low-set ears; asymmetric facial features, and large hands (Lubs 1969;von Reyn et al 1978). After mapping of this chromosomal variation to Xq27.3 (Harrison et al 1983) and confirming the fragile site in many families segregating ID, the disorder became known as fragile X syndrome (FXS). Affected males have moderate to severe ID,speechdelay,andmotorabnormalities.Common psychiatric features include hyperactivity, anxiety, and severe autism spectrum phenotypes.…”