The distribution of CY2PC19*2 allele in a Trinidadian population. Is Clopidogrel the right choice?

OBJECTIVE: To determine the distribution of the CYP2C19*2 allele among Trinidadians. DESIGN AND METHODS: This is a cross sectional study among 100 patients attending primary health centers within the North Central Region of Trinidad. A stratified sampling technique was used in which there were three mutually exclusive subgroups: those of South Asian descent (Indo-Trinidadians), African descent (Afro-Trinidadians) and mixed ethnicity. Subsequently, systematic sampling was applied to each stratum to improve the representativeness of the sample. Hence, the 100 subjects recruited for the study were 40 Indo-Trinidadians, 40 Afro-Trinidadians and 20 of mixed descent. Apart from baseline data which included age, gender and ethnicity, DNA was assessed for the CYP2C19*2 allelic variant using a PCR method. RESULTS: There was a high allelic frequency (37%) for CYP2C19*2 which was found to be more common among Indo-Trinidadians (47.5%, 95% CI 32.0-63.0) compared to Afro-Trinidadians (22.5%, 95% CI 9.6-35.4) or people of mixed origin (45%, 95% CI 23.2-66.8). There was a significant difference (p=0.019) between CYP2C19*2 frequencies for Indo-Trinidadians and Afro-Trinidadians. CONCLUSION: We provided evidence that the prevalence of CYP2C19*2 mutation was high in our setting.

Demographics of breast cancer in a small cohort of women in the Caribbean

OBJECTIVES: To address the prevalence and spectrum of breast cancer (BRCA1 and BRCA2) mutations in the Caribbean population. DESIGN AND METHODS: Demographic and clinical pathologic data was collected from 347 women of Afro-Caribbean decent. The cohort included women with breast cancer from the following countries: the Cayman Islands, Jamaica, Barbados, Dominica, Trinidad & Tobago and Haiti. RESULTS: The mean age of onset in the cohort was 48.1 yrs. with a mean body mass index (BMI) of 27.7. 70% of breast cancer cases were estrogen receptor-positive (ER+) (n=241) and in Jamaica 27% (n=105) of breast cancer cases were human epidermal growth factor receptor 2 positive (Her2+). Total Abdominal Hysterectomy Bilateral Salpingo Oophorectomy (TAH-BSO) delayed invasive breast cancer from 48 to 53 years (p=0.005). Parity was a significant factor (p<0.0001), which delayed age of onset by 8 yrs. Additionally, pregnancy alone delayed age of onset (p<0.005) by 8 yrs. Only three women out of 347 were found to have a mutation. CONCLUSIONS: This population-based study provided an insight into pattern of risk factors – both genetic and environmental of breast cancer incidence and subtype across the Caribbean. In conclusion 1) genetic causes of breast cancer appeared rare outside of the Bahamas, 2) fertility factors appeared important in the development of breast cancer, 3) TAH-BSO was common as both a form of contraception and because of the high incidence of fibroids, it may be protective, 4) BMI may impact on breast cancer development and 5) screening mammography was rare and the vast majority was diagnostic in nature.

Congenital afibrinogenemia: mutations leading to premature termination codons in fibrinogen AO-chain gene are not associated with the decay of the mutant mRNAs

Congenital afibrinogenemia is a rare coagulation disorder with autosomal recessive inheritance, characterized by the complete absence or extremely reduced levels of fibrinogen in patients, plasma and platlets. Eight afibrinogemic probands, with very low plasma levels of immunoreactive fibriogen were studied. Sequencing of the fibrinogen gene cluster of each proband disclosed 4 novel point mutations (1914C>G, 1193G> T, 1215delT, and 3075C> T) and 1 already reported (3192C>T). All mutations, localized within the first 4 exons of the AO-chain gene, were null mutations predicted to produce severely truncated AO-chains because of the presence of premature termination codons. Since premature termination codons are frequently known to affect the metabolism of the corresponding messenger RNAs (mRNAs), the degree of stability of each mutant mRNA was investigated. Contransfection experiments with plasmids expressing the wild type and each of the mutant AO-chains, followed by RNA extraction and semiquantative reversetranscriptase-polymerase chain reaction analysis, demonstrated that all the identified null mutations escaped nonsense-mediated mRNA decay. Moreover, ex vivo analysis at the protein level demonstrated that the presence of each mutation was sufficient to abolish fibrinogen sectretion. (AU)

Slipped-strand mispairing at noncontiguous repeats in Poecilia reticulata: a model for minisatellite birth

The standard slipped-strand mispairing (SSM) model for the formation of variable number tandem repeats (VNTRs) proposes that a few tandem repeats, produced by chance mutations, provide the "raw material" for VNTR expansion. However, this model is unlikely to explain the formation of VNTRs with long motifs (e.g., minisatellites), because the likelihood of a tandem repeat forming by chance decreases rapidly as the length of the repeat motif increases. Phylogenetic reconstruction of the birth of a mitochondrial (mt) DNA minisatellite in guppies suggests that VNTRs with long motifs can form as a consequence of SSM at noncontiguous repeats. VNTRs formed in this manner have motifs longer than the noncontiguous repeat originally formed by chance and are flanked by one unit of the original, noncontiguous repeat. SSM at noncontiguous repeats can therefore explain the birth of VNTRs with long motifs and the "imperfect" or "short direct" repeats frequently observed adjacent to both mtDNA and nuclear VNTRs.

Jamaican Sbetañthalassaemia: mutations and haematology

The sickling disorders are a common cause of morbidity and mortality in Jamaica. Sickle cell betañthalassaemia is the fourth commonest form, occuring in one in every 3000 births. This is a heterogeneous condition, producing HbS, HbF and HbA2 with variable amounts of HbA, depending on the mutation and, within a defined population, only a few beta-thalassaemia mutations occur at high frequency. This study establishes the frequency of beta-thalassaemia mutations in Sbetañthalassaemia patients in Jamaica. In addition, comparison of the haematological phenotypes is possible by looking at the "average steady-state haematology" of the different mutational groups. Blood samples from 132 unrelated Sbetañthalassaemia patients attending the MRC Sickle Cell Unit at the University of the West Indies were analysed by amplification refractory mutation system (ARMS) polymerase chain reaction (PCR) or sequencing to determine the nature and frequencies of the underlying beta-thalassaemia mutations. Ten mutations were identified, four of which accounted for 93 percent of the patients studied. These were 29 (A --> G) in 71 (54 percent), -88 (C --> T) in 27 (20 percent), polyA (T --> C) in 17 (13 percent) and IVS1-5 (G --> C) in nine (7 percent). The six remaining mutations found at lower frequency were C24 (T --> A) in two patients and one each of IVS2-848 (C --> A), -90 (C --> T), IVS1-5 (G --> T),IVS1-6 (T --> C). In one individual, no mutation was found. The three commonest mutations were all associated with levels of greater than 10 g/dl, whereas IVS1-5 (G --> C) had a more severe haematological phenotype. The predominance of -29 (A --> G) and -88 (C --> T) is in keeping with other studies on populations of African origin. IVS1-5 (G --> C) is found chiefly in Indian populations, and all affected families acknowledged Indian ancestry, reflecting the prominent Indian community in Jamaica. (AU)

Nucleotide sequence analysis of human T-cell lymphotropic virus type I pX and LTR regions from patients with sicca syndrome

Human T-cell lymphotropic virus type I (HTLV-I) is associated with adult T-cell leukemia (ATL) and tropical spastic paraparesis/HTLV-I-associated myelopathy (TSP/HAM). Other inflammatory disorders may occur in HTLV-I-infected patients, such as sicca syndrome resembling Sjogren's syndrome. The sicca syndrome may be the unique clinical manifestation of HTLV-I infection, but is associated frequently with TSP/HAM, which could suggest that sicca syndrome might be an early event in disease progression to TSP/HAM in some cases. We investigated whether peculiar pX and LTR mutations could be related to sicca syndrome, or might argue the existence of clinical progression to TSP/HAM. pX, especially pX(I), pX(II), and pX(IV) ORFs corresponding to Tax cytotoxic T-lymphocyte epitopes, and LTR regions from Caribbean patients who have sicca sydrome with or without TSP/HAM, ATL patients, and healthy carriers were sequenced. The sequences were aligned and compared with ATK-1 prototype and published sequences. LTR sequences exhibited 1.5-2.4 percent of divergence with ATK-1. pX-sequenced regions showed a lower homology within p12(I) encoding sequences. Only few mutations were found within functionally important regions, but were not associated specifically with the clinical status. Finally, no existence of clinical progression to TSP/HAM were found. It would be of interest to study the clinical evolution of HTLV-I-sicca syndrome in patients and to determine HTLV-I sequences from peripheral blood and salivary glands at different stages. Copyright 1999 Wiley-Liss, Inc.(Au)

The Trp64 A rg mutation of the B3- Adrenergic Receptor Is associated with hyperglycemia and current body mass index in Jamaican women

The Trp64Arg mutation the the beta3-adrenergic receptor (beta3-AR) has been linked to earlier onset of non-insulin-dependent diabetes mellitus (NIDDM), insulin resistance, abdominal obesity, and an increase capacity to gain weight in some European and Japanese populations. We studied the prevalence of the mutation and its association with NIDDM and obesity in our population, in which both rates are high, especially in women. The frequency of the homozygous mutation was 1.53 percent, and of the Arg allele, 10.5 percent. Rates were similar in men and women. Significantly higher body mass index (BMI), weight, hip circumference, and fasting and postchallenge 2 hour blood glucose concentrations were associated with the presence of the Arg allele in women but not in men. The association with weight and hip measurements and with hyperglycemia was present only in women aged less than 55 years. In multivariate analysis, the mutation was associated with the BMI and sex in a model that also included age. The variation in fasting and 2 hour blood glucose levels were predicted by beta3-AR, gender, age and BMI. These results suggest that the presence of the mutation contributes to obesity and hyperglycemia in our female population.(AU)

Obesity and dysglycaemia in Jamaican women: does the Trp64Arg mutation of B-3 adrenergic receptor play a role?

The Trp64Arg mutation of B3 adrenergic receptor (B3AR) has been linked to earlier onset of non insulin dependent diabetes (NIDDM), insulin resistance, abdominal obesity and increased capacity to gain weight in some European and Japanese populations. We studied the prevalence of the mutation and its association with NIDDM and obesity in our population in which both rates are high, especially in women. The frequency of the homozygous mutation was 1.53 percent and of the Arg allele, 10.5 percent. Rates were similar in males and females. Significantly higher levels of BMI weight, hip circumference, fasting and post challenge 2h blood glucose concentrations were associated with the presence of the Arg allele in women but not in men. The association with weight and hip measurements and with hyperglycaemia was present only in women >55 years. In multivariate analysis the mutation was associated with BMI and gender in a model that also included age. The variation in fasting and 2h blood glucose levels was predicted by B3 Ar, gender, age and MBI. These results suggest that the presence of the mutation contributes to obesity and hyperglycaemia in our female population. (AU)

Identification of a unique group of human papillomavirus type 16 sequence variants among clinical isolates from Barbados

The naturally occurring sequence variation of human papillomavirus type 16 (HPV-16) was analysed by direct sequence analysis of the PCR products of the long control region (LCR), the E5 and E7 open reading frames (OFRs), a segment of the L2 ORF overlapping the early viral poly(A) signal and a small segment of the L1 ORF or clinical isolates from Barbados and The Netherlands. Despite the widely different geographical and ethnic origin of the two groups of specimens, sequence analysis revealed relatively few mutational differences. Analysis of the LCR and the E5 ORF appeared to be the minimum requirement for the correct positioning of these variants in the HPV-16 phylogenetic tree. Most of the Barbadian variants appeared to be located at a unique position in the HPV-16 phylogenetic tree, at the internal branch close to the point where the European and Asian branches diverge. In contrast, most of the Dutch samples were located on the European branch. (AU)

G gamma beta+ hereditary persistence of fetal hemoglobin: cosmid cloning and identification of a specific mutation 5' to the G gamma gene

Hereditary persistence of fetal hemoglobin (HPFH) is a benign condition in which the normal shutoff of fetal hemoglobin (Hb F) production fails to occur. In the G gamma beta+ type of HPFH, erythrocytes of adult heterozygotes contain approximately equal to 20 percent Hb F, which is almost exclusively of the G gamma-globin variety, without increased levels of gamma-globin chains from the nearby A gamma-globin gene. Unlike some forms of HPFH, no major deletions in the globin gene cluster have been found by genomic blotting in the G gamma beta+ variety. We report here a family with this condition, from which cosmid clones of the beta-globin gene cluster from the G gamma beta+ HPFH allele have been obtained. Sequencing around the fetal genes has identified a point mutation 202 base pairs 5' to the G gamma-globin gene that is present in genomic DNA of 3/3 unrelated individuals with G gamma beta+ HPFH but in none of more than 100 non-HPFH individuals. Although the mutation could represent a tightly linked polymorphism, its location in a region suggested by recent data to be important in tissue-specific control of gene expression suggests the possibility that the -202 mutation accounts for the phenotype. The sequence created resembles elements of other eukaryotic promoters known to be important for efficient transcription. (AU)

Origin of the beta S-globin gene in blacks: the contribution of recurrent mutation or gene conversion or both

In order to investigate the origin(s) of the mutation(s) leading to the beta S-globin gene in North American populations of African ancestory, we analysed DNA polymorphisms in the beta-globin gene cluster in a large number of both beta A- and beta S-globin gene-bearing chromosomes in U.S. and Jamaican Blacks. We found 16 different haplotypes of polymorphic sites associated with 170 beta S-globin gene-bearing chromosomes. The three most common beta S haplotypes, which account for 151/170 of the beta S-globin gene-bearing chromosomes, are only rarely seen in the chromosomes bearing the beta A-globin gene in these populations (6/47). Two observations suggest multiple origins or interallelic gene conversion, or both, of the beta S mutation. First, the mutation is present in all three beta-globin gene frameworks. Second, the beta S haplotypes can be divided into four groups, each of which cannot be derived from any other by less than two crossing-over events. In summary, our observation of the beta S mutation on 16 different halotypes in African populations can be best explained by (i) a number of simple recombination events 5' to the beta-globin gene and (ii) up to four independent mutations and/or interallelic gene conversions. (AU)

In-born errors of metabolism

The causes of the majority of in-born errors of metabolism have yet to be fully elucidated, further knowledge of the mechanisms of these lethal metabolic disorders is necessary in order to employ adequate therapy. A very interesting line of therapy was observed in a recent paper by Schneck et al who diagnosed Tay Sach's disease after ammniocentesis, and subsequently terminated the pregnancy. Prevention to my mind could in the future be the primary aim of therapy in certain of these lethal disorders rather than one subjecting himself to the pros and cons and the psychological trauma of euthanasia. It would also be interesting to see how far prenatal diagnosis could go to aid the prevention of lethal haemoglobinopathies. The concept of prevention within this concept without doubt poses a serious ethical problem. (Summary)