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Gaucher disease is the most prevalent lysosomal storage disease and it results from inherited deficient glucocerebrosidase activity. The glucocerebrosidase gene from normal people was sequenced by several laboratories and it was noted that a G or A nucleotide may be present at cDNA position 1601, resulting in 495arginine or 495histidine in the glucocerebrosidase polypeptide. In order to rule out the possibility of cloning error and to elucidate the genetic status of the two genotypes and their distribution in the population, we have developed a convenient and reliable method for the molecular screening of the 1601G and 1601A genotypes in the population. This method uses PCR amplification of glucocerebrosidase genomic DNA in blood samples, followed by BsaHI restriction fragment length polymorphism analysis. Out of the 256 subjects without Gaucher disease and 15 Gaucher patients surveyed, the 1601G genotype was present in the homozygous form in all of the asymptomatic subjects and 14 Gaucher patients. In one Gaucher patient who was diagnosed as having type 1 (non-neuropathic) Gaucher disease with the A1226G/T1366G mutations, the heterozygous 1601G/A genotype was detected. These findings indicate that the 1601G genotype which encodes 495arginine of the glucocerebrosidase polypeptide is not a cloning error. Instead, it constitutes the normal as well as predominant genotype in the population in the municipality of Greater Victoria, British Columbia. The 1601A genotype, on the other hand, appears to be quite infrequent in this population. The availability of our restriction enzyme based method has allowed the screening and frequency determination of these two alleles in other populations.

Type 1 Gaucher disease families were studied in an attempt to establish a phenotype/genotype correlation in affected persons and also to identify carriers accurately. In the Portuguese type 1 Gaucher patients, screening for mutations N370S, L444P, R463C, and 1066 + 1 G-->A allowed the identification of 85% of the alleles among unrelated patients. A subclinical case with genotype N370S/1066 + 1 G-->A was identified in one family in which there were three other symptomatic sibs. To our knowledge this is the first subclinical case with a genotype other than N370S/N370S. No genotype-phenotype correlation could be established and considerable clinical heterogeneity was found even among sibs with the same genotype. The data collected on the origins of the Gaucher families indicated two areas in northern Portugal where a higher frequency of the disease may be expected to exist.

The adult non-neuropathic form of Gaucher's disease has been identified in 32 patients in 25 Ashkenazi Jewish kindreds in South Africa. The minimum prevalence in this population is 1 in 5000, with a gene frequency of 0.014 and a carrier rate of 1 in 36. On correction for bias resulting from possible under-ascertainment, these minimum figures become 1 in 4000, 0.0166, and 1 in 30, respectively. Confirmation of autosomal recessive inheritance was obtained by segregation analysis by the 'a priori' and 'simple sib' methods. The Ashkenazin of South Africa have their origins in Lithuania and it is evident that the high gene frequency in South Africa is a reflection of the genetic constitution of the immigrant population. The localisation of the Gaucher gene to Lithuania represents a further step in the determination of the early geographic distribution of the genetic disorders of the Jewish race.