ABSTRACT
Small supernumerary marker chromosomes (sSMCs) are structurally abnormal chromosomes that cannot be characterized by karyotype. In many prenatal cases of de novo sSMC, the outcome of pregnancy is difficult to predict because the euchromatin content is unclear. This study aimed to determine the presence or absence of euchromatin material of 39 de novo prenatally ascertained sSMC by array-comparative genomic hybridization (array-CGH) or single nucleotide polymorphism (SNP) array. Cases were prospectively ascertained from the study of 65,000 prenatal samples [0.060%; 95% confidence interval (CI), 0.042-0.082]. Array-CGH showed that 22 markers were derived from non-acrocentric markers (56.4%) and 7 from acrocentic markers (18%). The 10 additional cases remained unidentified (25.6%), but 7 of 10 could be further identified using fluorescence in situ hybridization; 69% of de novo sSMC contained euchromatin material, 95.4% of which for non-acrocentric markers. Some sSMC containing euchromatin had a normal phenotype (31% for non-acrocentric and 75% for acrocentric markers). Statistical differences between normal and abnormal phenotypes were shown for the size of the euchromatin material (more or less than 1 Mb, p = 0.0006) and number of genes (more or less than 10, p = 0.0009). This study is the largest to date and shows the utility of array-CGH or SNP array in the detection and characterization of de novo sSMC in a prenatal context.
Subject(s)
Chromosome Aberrations , Genetic Counseling , Genetic Predisposition to Disease , Prognosis , Adult , Comparative Genomic Hybridization , Female , France , Genetic Association Studies , Genetic Markers , Genome-Wide Association Study , Humans , In Situ Hybridization, Fluorescence , Karyotype , Middle Aged , Polymorphism, Single Nucleotide , Pregnancy , Prenatal Diagnosis , Prospective Studies , Risk , Switzerland , Young AdultABSTRACT
Four groups of 10 male rats (Group A: normal rats, Group B: castrated rats, Group C: castrated rats + 1 mg P.T./day, Group D: castrated rats + 1 dose of 50 mg/kg of P.T. cyclohexane) were avoidance conditioned during nine sessions of 50 trials. They were conditioned individually during sessions 4, 5 and 6 and by pairs during sessions 1, 2, 3, 7, 8 and 9. During these last sessions, all groups presented a low level of acquisition and aggressive behaviour. These phenomena were worsened in the castrated rats whose performances stayed low even when they were conditioned individually. On the other hand, the frequency of their aggressive behaviour was often higher than that of the other groups. The injection of P.T. cyclo-hexane improves the performance of the castrated animals but does not entirely compensate for the differences between control and experimental rats.
