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[Genetic background of retinoblastoma].

Retinoblastoma is a malignant tumour of the eye ball, which develops as a result of the mutation of both alleles of RB-1 gene. Molecular mechanisms and their implications in clinical diagnosis and genetic counselling in retinoblastoma families are discussed.

Genetic Counseling↗
PubMed2003

[Genetic background of osteoporosis].

Osteoporosis is characterized by a decrease in bone mass as well as a deterioration of the bone architecture resulting in an increased risk of fracture. The disease is multifactorial, and it depends on environmental and genetic factors. Twin studies have shown that genetic factors account for 60-80% of the variance in bone mineral density, the best predictor of the risk of osteoporosis. There are different approaches to identify these genetic factors. Linkage studies in human and experimental animals have defined multiple loci that regulate bone mass but most of the genes responsible for this effect remain to be defined. The 11q12-13 locus was the first that was linked to bone mineral density of the young female and special bone diseases like high bone mass syndrome and osteoporosis-pseudoglioma syndrome. Both diseases appear to be in association with LDL receptor-related protein 5 gene mutation. The effect of LDL receptor-related protein 5 on bone metabolism had not been known only genetic methods suggested it. The effect of LRP5 in osteoporosis pathogenesis requires more investigation. Association and linkage studies have been performed in order to identify candidate genes in the pathogenesis of osteoporosis. Vitamin D receptor gene was the first candidate, however its effect is controversial. Other candidates, such as insulin like growth factor, interleukin-6, estrogen receptor alpha, transforming growth factor beta show no or small effect on bone mineral density or fracture frequency. To date only Sp1 polymorphism of collagen gene seems to have a consistent effect on bone fragility. The improved understanding of osteoporosis genetics should lead to better diagnosis of this disease and new treatment and prevention strategies.

Animals↗
PubMed2026

Waist-to-height ratio as a practical indicator for screening pediatric metabolic dysfunction-associated steatotic liver disease in diverse populations and genetic backgrounds.

BACKGROUND: Metabolic dysfunction-associated steatotic liver disease (MASLD) is the leading chronic liver disease in children and adolescents; this parallels the global obesity epidemic. The contribution of genetic susceptibility to pediatric MASLD, and its interaction with anthropometric and biochemical indices used for non-invasive screening remains poorly understood. We aimed to evaluate waist-to-height ratio (WHtR) as a simple, equitable, and scalable tool for early identification of pediatric MASLD and relate this to genetic risk. METHODS: We combined school-based data from 1010 Chinese children with analyses of the Global Burden of Disease, the 1000 Genomes Project, and the US National Health and Nutrition Examination Survey (NHANES). Thirteen MASLD-related single-nucleotide polymorphisms (SNPs) were genotyped to construct a genetic risk score (GRS). We examined global epidemiological patterns, quantified inter-population allele divergence, and assessed how GRS modifies cutoffs and performance of nine anthropometric and biochemical indices. RESULTS: Genetic analysis revealed minimal frequency divergence across most ancestries (mean Fixation index&#x2009;<&#x2009;0.05), except for the African ancestry where there was moderate divergence. Higher GRS were associated with lower cutoffs across indices. When GRS Z-score increased from -3 to 3, visceral adiposity index showed the sharpest changes (Z-score decreased from 1.5 to -1.8), while BFP (1.2&#xa0;to&#xa0;0.1) and WHtR (1.5&#xa0;to&#xa0;0.1) showed gradual change. Furthermore, incorporating GRS into the base anthropometric models yielded only marginal improvements in overall screening performance [area under the receiver operating characteristic curve (AUC) and Youden Index]. Validation in NHANES showed WHtR&#x2009;&#x2265;&#x2009;0.48 retained high discrimination (AUC&#x2009;>&#x2009;0.87) across most genetic variants. CONCLUSIONS: This study suggests that WHtR is a consistent and practical tool for screening pediatric patients with MASLD across diverse populations. While genetic variation may influence optimal thresholds, WHtR&#x2009;&#x2265;&#x2009;0.48 appears broadly applicable, supporting its potential use as a frontline screening metric in diverse settings.

Humans↗
PubMed2006

The contributions of normal variation and genetic background to mammalian gene expression.

BACKGROUND: Qualitative and quantitative variability in gene expression represents the substrate for external conditions to exert selective pressures for natural selection. Current technologies allow for some forms of genetic variation, such as DNA mutations and polymorphisms, to be determined accurately on a comprehensive scale. Other components of variability, such as stochastic events in cellular transcriptional and translational processes, are less well characterized. Although potentially important, the relative contributions of genomic versus epigenetic and stochastic factors to variation in gene expression have not been quantified in mammalian species. RESULTS: In this study we compared microarray-based measures of hepatic transcript abundance levels within and between five different strains of Mus musculus. Within each strain 23% to 44% of all genes exhibited statistically significant differences in expression between genetically identical individuals (positive false discovery rate of 10%). Genes functionally associated with cell growth, cytokine activity, amine metabolism, and ubiquitination were enriched in this group. Genetic divergence between individuals of different strains also contributed to transcript abundance level differences, but to a lesser extent than intra-strain variation, with approximately 3% of all genes exhibiting inter-strain expression differences. CONCLUSION: These results indicate that although DNA sequence fixes boundaries for gene expression variability, there remain considerable latitudes of expression within these genome-defined limits that have the potential to influence phenotypes. The extent of normal or expected natural variability in gene expression may provide an additional level of phenotypic opportunity for natural selection.

Animals↗
PubMed2005

Genetic loci for ventricular dilatation in the LEW/Jms rat with fetal-onset hydrocephalus are influenced by gender and genetic background.

BACKGROUND: The LEW/Jms rat strain has inherited hydrocephalus, with more males affected than females and an overall expression rate of 28%. This study aimed to determine chromosomal positions for genetic loci causing the hydrocephalus. METHODS: An F1 backcross was made to the parental LEW/Jms strain from a cross with non-hydrocephalic Fischer 344 rats. BC1 rats were generated for two specific crosses: the first with a male LEW/Jms rat as parent and grandparent, [(F x L) x L], designated B group, and the second with a female LEW/Jms rat as the parent and grandparent [L x (L x F)], designated C group. All hydrocephalic and a similar number of non-hydrocephalic rats from these two groups were genotyped with microsatellite markers and the data was analyzed separately for each sex by MAPMAKER. RESULTS: The frequency of hydrocephalus was not significantly different between the two groups (18.2 and 19.9 %), but there was a significant excess of males in the B group. The mean severity of hydrocephalus, measured as the ventricle-to-brain width ratio, was ranked as B group < C group < LEW/Jms. For the both rat groups, there were several chromosomes that showed possible regions with association between phenotype and genotype significant at the 5% or 1.0% level, but none of these had significant LOD scores. For the C group with a female LEW/Jms parent, there was a fully significant locus on Chr2 with a LOD score of 3.81 that was associated almost exclusively with male rats. Both groups showed possible linkage on Chr17 and the data combined produced a LOD score of 2.71, between suggestive and full significance. This locus was largely associated with male rats with a LEW/Jms male parent. CONCLUSION: Phenotypic expression of hydrocephalus in Lew/Jms, although not X-linked, has a strong male bias. One, and possibly two chromosomal regions are associated with the hydrocephalus.

Journal Article↗
PubMed1994

On the genetic background of the adaptive response to X-rays in Drosophila melanogaster.

The effects of a low dose (0.1-20 mGy) preirradiation with X-rays followed by a higher dose (2 Gy) of the same radiation on the recovery of the genetic damage induced as dominant lethals in mature oocytes (stage 14) of different strains of Drosophila melanogaster were investigated. The response was shown to be dependent on the genotype of the flies tested, since lower frequencies of dominant lethals (DL) were only obtained in strains carrying the white mutation. Based on these observations experiments to locate the genetic factor responsible for the adaptive response (AR) were performed. This factor was found to be in a specific region of the X-chromosome. Additional experiments were carried out to give information on the minimal dose required to induce the AR. The results showed that the lowest dose needed is 0.2 mGy. Increasing the conditioning X-ray dose had no influence on the response.

Adaptation, Physiological↗