Anticipation (genetics)

About: Anticipation (genetics) is a research topic. Over the lifetime, 669 publications have been published within this topic receiving 21784 citations. The topic is also known as: Genetic Anticipation & Anticipation, Genetic.

Germline novel MSH2 deletions and a founder MSH2 deletion associated with anticipation effects in HNPCC

Abstract: Hereditary non-polyposis colorectal cancer (HNPCC) is caused by inactivating mutations of DNA mismatch repair genes. Large genomic rearrangements in these genes have been increasingly recognized as important causes of HNPCC. Using multiplex ligation-dependent probe amplification, we identified three MSH2 deletions in Italian patients with HNPCC (proband A: exons 1-3, proband M: exon 8, and proband C: exons 1-6). Deletion breakpoint sequencing allowed us to develop rapid polymerase chain reaction-based mutation screening, which confirmed the presence of the deletions in affected and asymptomatic individuals of families A, C, and M. While the exon 8 and exon 1-3 deletions appear to be novel, the MSH2 1-6 deletion found in family C is identical to the one recently documented in two branches of another unrelated Italian family (family V+Va). Haplotype analysis showed that the kindreds C and V+Va (both from northeastern Italy, both displaying clinical features of the Muir-Torre syndrome) shared a seven-locus haplotype, indicating that the MSH2 1-6 deletion is probably a founder mutation. Families A, C, M, and V+Va all showed progressively earlier cancer-onset ages in successive generations. Analysis of 23 affected parent-child pairs in the four kindreds showed median anticipation of 12 years in offsprings' onset of cancer (p = 0.0001). No birth cohort effect was found. This is the first significant evidence of anticipation effects in HNPCC families carrying MSH2 deletions.

Clustering of ALS patients in central Italy due to the occurrence of the L84F SOD1 gene mutation.

Abstract: Objective: To study three new apparently unrelated Italian families with ALS and several sporadic ALS patients living in the same rural area. Background: One Italian family with ALS carrying a superoxide dismutase 1 (SOD1) gene mutation (G41S) and no regional ALS clustering has been reported in Italy. Methods: Genetic analysis was performed by automated and manual sequencing of the SOD1 gene in 13 family members and in 6 of 10 unrelated patients with sporadic cases of ALS living in the same area. The authors also determined SOD1 activity in erythrocytes and lymphocytes. Results: The three families included a total of 28 affected members distributed over six generations. Despite a wide variability in age at onset and disease duration, the clinical pattern is uniform, with onset in the lower limbs, ascending progression, and predominant lower motor neuron involvement in all subjects. Generational anticipation is evident in the last two generations. All familial ALS patients and one of the six sporadic patients carry the same L84F missense point mutation in exon 4 of the SOD1 gene. SOD1 enzyme activity and SOD1 protein levels were not decreased significantly in the L84F patients. Conclusion: The ALS patients carrying the L84F mutation derive from a common ancestor. This mutation is responsible for ALS clustering in the area. The L84F mutation does not modify SOD1-specific activity.

Myotonic dystrophy type 1.

Abstract: The prevalence of myotonic dystrophy type 1 ranges between 0.5 and 18.1 per 100 000 population, making it the most common muscular dystrophy, ahead of Duchenne and facioscapulohumeral muscular dystrophies.[1][1] Myotonic dystrophy type 1 is especially prevalent in certain regions of Quebec.[2][2] It

Familial Mental Retardation Syndrome ATR-16 Due to an Inherited Cryptic Subtelomeric Translocation, t(3;16)(q29;p13.3)

Abstract: In the search for genetic causes of mental retardation, we have studied a five-generation family that includes 10 individuals in generations IV and V who are affected with mild-to-moderate mental retardation and mild, nonspecific dysmorphic features. The disease is inherited in a seemingly autosomal dominant fashion with reduced penetrance. The pedigree is unusual because of (1) its size and (2) the fact that individuals with the disease appear only in the last two generations, which is suggestive of anticipation. Standard clinical and laboratory screening protocols and extended cytogenetic analysis, including the use of high-resolution karyotyping and multiplex FISH (M-FISH), could not reveal the cause of the mental retardation. Therefore, a whole-genome scan was performed, by linkage analysis, with microsatellite markers. The phenotype was linked to chromosome 16p13.3, and, unexpectedly, a deletion of a part of 16pter was demonstrated in patients, similar to the deletion observed in patients with ATR-16 syndrome. Subsequent FISH analysis demonstrated that patients inherited a duplication of terminal 3q in addition to the deletion of 16p. FISH analysis of obligate carriers revealed that a balanced translocation between the terminal parts of 16p and 3q segregated in this family. This case reinforces the role of cryptic (cytogenetically invisible) subtelomeric translocations in mental retardation, which is estimated by others to be implicated in 5%-10% of cases.

Age of onset evidence for anticipation in familial non-Hodgkin's lymphoma.

Abstract: Anticipation, a phenomenon in which an inherited disease is diagnosed at an earlier age in each successive generation of a family, has been demonstrated in certain neurological and haematological disorders. This study was conducted to determine whether anticipation occurs in familial non-Hodgkin's lymphoma (NHL). Eleven published reports of multigenerational familial NHL were analysed for evidence of anticipation, together with 18 previously unreported families with familial NHL. Differences in disease-free survival between generations were determined. The difference between age at onset for each affected parent–child pair was tested against the null hypothesis that there was no difference in age at onset. These analyses were also performed separately using only parent–child pairs with age of onset > 25 years to avoid ascertainment bias. In addition, the age at onset distribution of the studied cases was compared with that of the Surveillance Epidemiology and End Results (SEER) Program using data for 1973–98. The median ages at onset in the child and parent generations of all families (48.5 and 71.3 years respectively) and in the selected pairs (52.5 and 71.5 years respectively) were significantly different (P < 0.000002 and P < 0.000001 respectively). The null hypothesis was rejected for all (P < 0.000001) as well as selected pairs (P < 0.000003). A significant difference was observed between the ages of onset of the child generation and the SEER population (P < 0.009), but not between the parent generation and the SEER population. Anticipation occurs in familial NHL, which suggests a genetic basis for it.