Familial partial trisomy 5p resulting from segregation of an insertional translocation

A case of duplication of segment p13-p15 of the short arm of chromosome 5 as the result of an insertional translocation in a mentally retarded girl with congenital anomalies is reported. Some of the apparently balanced carriers of the inverted insertion showed minor congenital anomalies.     

Complex evolution of X and Y autosomal translocations in the giant mole-rat, Cryptomys mechowi (Bathyergidae)

Cross-species chromosome painting was used to determine homologous chromosomal regions between two species of mole-rat, the naked mole-rat, Heterocephalus glaber (2n = 60), and the giant mole-rat, Cryptomys mechowi (2n = 40), using flow-sorted painting probes representative of all but two of the H. glaber chromosomal complement. In total 43 homologous regions were identified in the C. mechowi genome. Eight H. glaber chromosomes are retained in toto in C. mechowi, and 13 produce two or more signals in this species. The most striking difference in the karyotypes of the two taxa concerns their sex chromosomes. The H. glaber painting probes identified a complex series of translocations that involved the fractionation of four autosomes and the subsequent translocation of segments to the sex chromosomes and to autosomal partners in the C. mechowi genome. An intercalary heterochromatic block (IHB) was detected in sex chromosomes of C. mechowi at the boundary with the translocated autosomal segment. We discuss the likely sequence of evolutionary events that has led to the contemporary composition of the C. mechowi sex chromosomes, and consider these in the light of prevailing views on the genesis of sex chromosomes in mammals.     

运用全染色体探针FISH技术进行罗伯逊易位携带者胚胎植入前诊断

目的运用全染色体探针荧光原位杂交技术(fluorescent in situ hybridization ,FISH)对14/21罗伯逊易位携带者的胚胎进行植入前遗传学诊断,达到优生目的.方法应用FITC、Texas标记的21/14全染色体探针对14/21罗伯逊易位携带者的胚胎活检后的单个卵裂球进行遗传学检测,选择正常信号或携带者信号核型胚胎进行移植.结果常规单精子显微注射-胚胎移植(intracytoplasmic sperm injection,ICSI)后获取胚胎12个,活检优质胚胎11个,杂交后有信号胚胎7个,其中1个正常胚胎,1个携带者胚胎;1个14单体胚胎,1个21单体胚胎,1个21三体胚胎,另2个胚胎活检后均为21号二体,无14号信号.结论运用14/21全染色体探针荧光原位杂交技术对14/21罗伯逊易位携带者的胚胎进行植入前遗传学诊断是能够将正常核型胚胎挑选出来进行移植,从而达到优生目的.     

Trisomy 17p due to a t(8; 17) (p23; p11.2)pat translocation. Case report and review of the literature

We describe a female newborn girl with partial trisomy 17p, which was not detected at the initial cytogenetic investigation, but which later proved to be an unbalanced product of a paternal translocation t(8; 17)(p23;pl 1.2). Comparison with the three previously reported patients suggests a clinically distinct "trisomy 17p syndrome", i.e. pre- and postnatal growth retardation, microcephaly, antimongoloid slanting of palpebral fissures, hypertelorism, long philtrum with thin upper lip, micrognathia and high-arched palate. Two of the four patients had a heart defect, and psychomotor developmental delay was evident in all four cases. In the present patient, the chromosomal anomaly was only detected after the finding of the autosomal reciprocal translocation in the father. The importance of cytogenetic investigations in parents of a MCA/MR child with apparently normal chromosomes is emphasized.     

Telomere-specific fluorescence in situ hybridization analysis of couples with five or more recurrent miscarriages

Fluorescence in situ hybridization analysis using telomere specific probes has been used to detect cryptic translocations in the chromosomal telomeric regions. This study was performed in five clinically normal couples who have had five or more spontaneous abortions and whose karyotypes were found to be normal using conventional cytogenetic techniques. Using the telomere specific probes, in one couple we determined a cryptic translocation between chromosome 3 and 10, and, in another couple, the signal in chromosome 20 was detected in another chromosome, which was probably a D group chromosome. Additionally, in the latter and also in two other couples, we observed a polymorphism. The approach will be helpful for screening cryptic translocations using telomere specific multiple probe sets in couples with recurrent miscarriages. As prenatal diagnosis will be available for these couples for future pregnancies, it will be possible to help these families to have healthy fetuses.     

Chromosome 1q terminal deletion resulting fromde novo translocation with an acrocentric chromosome

Summary Distal deletion of chromosome 1q has been reported in nearly 30 patients, all being associated with a deletion ranging from the 1q42 or q43 band to 1qter region. Here, we describe a girl with 1q terminal deletion resulting from an unbalancedde novo translocation t(1;D or G)(q44; p11), as revealed by the presence of a satellited feature and an NOR-stained region at the tip of 1q. We suggest that most of the phenotypic abnormalities seen in patients with 1q distal deletion are attributable to the monosomy for band 1q44.     

Systematic characterisation of disease associated balanced chromosome rearrangements by FISH: cytogenetically and genetically anchored YACs identify microdeletions and candidate regions for mental retardation genes

Disease associated balanced chromosome rearrangements (DBCRs) have been instrumental in the isolation of many disease genes. To facilitate the molecular cytogenetic characterisation of DBCRs, we have generated a set of >1200 non-chimeric, cytogenetically and genetically anchored CEPH YACs, on average one per 3 cM, spaced over the entire human genome. By fluorescence in situ hybridisation (FISH), we have performed a systematic search for YACs spanning translocation breakpoints. Patients with DBCRs and either syndromic or non-syndromic mental retardation (MR) were ascertained through the Mendelian Cytogenetics Network (MCN), a collaborative effort of, at present, 270 cytogenetic laboratories throughout the world. In this pilot study, we have characterised 10 different MR associated chromosome regions delineating candidate regions for MR. Five of these regions are narrowed to breakpoint spanning YACs, three of which are located on chromosomes 13q21, 13q22, and 13q32, respectively, one on chromosome 4p14, and one on 6q25. In two out of six DBCRs, we found cytogenetically cryptic deletions of 3-5 Mb on one or both translocation chromosomes. Thus, cryptic deletions may be an important cause of disease in seemingly balanced chromosome rearrangements that are associated with a disease phenotype. Our region specific FISH probes, which are available to MCN members, can be a powerful tool in clinical cytogenetics and positional cloning.     

Whole-arm reciprocal translocation (WART) between Robertsonian chromosomes: finding of a Robertsonian heterozygous mouse with karyotype derived through WARTs

The karyotype of a mouse trapped in a hybrid zone between a Robertsonian (Rb) population (2n=22) and a population with the standard karyotype (2n=40-all-telocentrics) shows two Rb chromosomes with new arm compositions. We suggest that whole-arm reciprocal translocations between Rb chromosomes gave rise to the new chromosome constitution and that such events can greatly help in understanding house mouse karyotype diversification and chromosomal speciation.     

Genetic aspects of animal reasoning

This paper reviews the investigations of Prof. L. V. Krushinsky and his colleagues into the genetics of complex behaviors in mammals. The ability of animals to extrapolate the direction of a food stimulus movement was investigated in wild and domesticated foxes (including different fur-color mutants), wild brown rats, and laboratory rats and mice. Wild animals (raised in the laboratory) were shown to be superior to their respective domesticated forms on performance of the extrapolation task, especially in their scores for the first presentation, in which no previous experience could be used. Laboratory rats and mice demonstrated a low level of extrapolation performance. This means that only a few laboratory animals were capable of solving the task, i.e., the percentage of correct solutions was equivalent to chance. The brain weight selection program resulted in two mice strains with a 20% (90-mg) difference in brain weight. Ability to solve the extrapolation task was present in low-brain weight mice in generations 7–11 but declined with further selection. Investigation of extrapolation ability in mice with different chromosomal anomalies demonstrated that animals with Robertsonian translocations Rb(8,17) 1lem and Rb(8,17) 6Sic were capable of solving this task in a statistically significant majority of cases, while mice with fusion of other chromosomes, as well as CBA normal karyotype mice, performed no better than expected by chance. Mice with two types of partial trisomies and animals homo- and heterozygous for translocations were also tested. Although mice with T6 trisomy performed no better than expected by chance, animals with trisomy for a chromosome 17 fragment solved the task successfully. Thus, a genetic component underlying the ability to solve the extrapolation task was demonstrated in three animal species. The extrapolation task in animals is considered to reveal a general capacity for elementary reasoning. The genetic basis of this capacity is very complex.     

Pallister-Hall syndrome associated with an unbalanced chromosome translocation

We report 3 cases of Pallister-Hall syndrome involving hypothalamic hamartoblastoma, hypopituitarism, cranial, and limb abnormalities. The first 2 cases represent the first apparent sibs reported with this syndrome. Patient 1 represents the first known patient with this syndrome with an abnormal karyotype.