A bstract To date, the identification of patients and earn ers of the fragile X syndrome has been earned out by DNA analysis by means of the polymerase chain reaction and Southern biot analysis. This direct DNA analysis al lows both the size of the CGG repeat and inethylation sta tus of the FMRI gene to be determined. We have recently presented a rapid antibody test on blood smears based on the presence of FMRP, the protein product of the FMRI gene, in lymphocytes from normal individuals and the ab sence of FMRP in lymphocytes from patients. Here, we have tested the diagnostic value of this new technique by studying FMRP expression in 173 blood smears from nor mal individuals and fragile X patients. The diagnostic power of the antibody test is "perfect" for males, whereas the results are less specific for females.

Aims-High quality RNA isolation from cartilaginous tissue is considered diYcult because of relatively low cellularity and the abundance of extracellular matrix rich in glycosaminoglycans and collagens. Given the growing interest and technical possibilities to study RNA expression at a high throughput level, research on tissue with these characteristics is hampered by the lack of an eYcient method for obtaining suYcient amounts of high quality RNA. Methods-This paper presents a robust protocol combining two RNA isolation procedures, based on a combination of Trizol and RNA specific columns, which has been developed to obtain high molecular weight RNA from fresh frozen and stored tissue of normal cartilage and cartilaginous tumours. Using this method, RNA was isolated from normal cartilage, peripheral chondrosarcoma, and central chondrosarcoma. Results-The yields ranged from 0.1 to 0.5 µg RNA/mg tissue. RNA isolated with this method was stable and of high molecular weight. RNA samples from normal cartilage and from two chondrosarcomas isolated using this method were applied successfully in cDNA microarray experiments. The number of genes that give interpretable results was in the range of what would be expected from microarray results obtained on chondrosarcoma cell line RNA. Signal to noise ratios were good and diVerential expression between tumour and normal cartilage was detectable for a large number of genes. Conclusion-With this newly developed isolation method, high quality RNA can be obtained from low cellular tissue with a high extracellular matrix component. These procedures can also be applied to other tumour material. (J Clin Pathol 2001;54:778-782)

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