Mapping of 29 YAC clones and identification of 3 YACs spanning the translocation t(3;8)(p14.2;q24.1) breakpoint at 8q24.1 in hereditary renal cell carcinoma

Fluorescent in situ hybridization of DNA probes in the interphase and metaphase stages of the cell cycle

In the past decade, fluorescent in situ hybridization (FISH) has been used routinely in detecting molecular abnormalities in the interphase and metaphase stages of the cell cycle. Many of the molecular anomalies which are detected in this manner are diagnostic of a prenatal, postnatal, or neoplastic genetic disorder. With the continuous isolation of commercially available DNA probes specific to a particular chromosome region, FISH analysis has become standardized in its ability to detect characteristic chromosomal anomalies in association with genetic and neoplastic diseases. In recent years, FISH has also become automated to accommodate the increased volume of slide preparations necessary for the number of DNA probes needed to detect characteristic molecular anomalies in cancer tissues and bone marrow samples. FISH technology provides essential information to the physician regarding the diagnosis, response to treatment, and ultimately the prognosis of their patients' disorder. It has become an important source of information routinely used in conjunction with chromosome analyses, and presently to confirm molecular alterations detected by array comparative genomic hybridization (aCGH) analyses. In this chapter we describe the methods for performing FISH analyses in order to determine the presence or the absence of genetic abnormalities which define whether the patient has either a genetic syndrome or malignant disease.

Dextrocardia, atrial septal defect, severe developmental delay, facial anomalies, and supernumerary ribs in a child with a complex unbalanced 8;22 translocation including partial 8p duplication

We report on a child with dextrocardia, atrial septal defect (ASD), severe developmental delay, hypotonia, 13 pairs of ribs, left preauricular choristoma, hirsutism, and craniofacial abnormalities. Prenatal cytogenetic evaluation showed karyotype 46,XY,?dup(8p)ish del(8)pter. Postnatal array CGH demonstrated a 6.8 Mb terminal deletion at 8p23.3-p23, an interstitial 31.1 Mb duplication within 8p23.1-p11, and a terminal duplication of 0.24 Mb at 22q13.33, refining the karyotype to 46,XY,der(8)dup(8)(p23.1p11.1)t(8;22)(p23.1;q13.1).ish der(8)dup(8)(p23.1p11.1)t(8;22)(p23.1;q13.1) (D8S504-,MS607 + ,ARSA + ,D8Z1 + , RP115713 + +). Previous reports of distal 8p deletion, 8p duplication, and distal 22q duplication have shown similar manifestations, including congenital heart disease, intellectual impairment, and multiple minor anomalies. We correlate the patient's clinical findings with these particular areas of copy number. This case study supports the use of aCGH to identify subtle chromosomal rearrangement in infants with cardiac malformation as their most significant or only apparent birth defect. Additionally, it illustrates why aCGH is essential in the description of chromosome rearrangements, even those seemingly visible via routine karyotype. This method shows that there is often greater complexity submicroscopically, essential to an adequate understanding of a patient's genotype and phenotype.

Origin of renal cell carcinomas

Cancer is a heritable disorder of somatic cells: environment and heredity are both important in the carcinogenic process. The primal force is the "two hits" of Knudson's hypothesis, which has proved true for many tumours, including renal cell carcinoma. Knudson et al. [1, 2] recognised that familial forms of cancer might hold the key to the identification of important regulatory elements known as tumour-suppressor genes. Their observations (i.e., that retinoblastoma tend to be multifocal in familial cases and unifocal in sporadic presentation) led them to propose a two-hit theory of carcinogenesis. Furthermore, Knudson postulated that patients with the familial form of the cancer would be born with one mutant allele and that all cells in that organ or tissue would be at risk, accounting for early onset and the multifocal nature of the disease. In contrast, sporadic tumours would develop only if a mutation occurred in both alleles within the same cell, and, as each event would be expected to occur with low frequency, most tumours would develop late in life and in a unifocal manner [3, 4]. The kidney is affected in a variety of inherited cancer syndromes. For most of them, both the oncogene/tumour-suppressor gene involved and the respective germline mutations have been identified. Each of the inherited syndromes predisposes to distinct types of renal carcinoma. Families with hereditary predisposition to cancer continue to provide a unique opportunity for the identification and characterisation of genes involved in carcinogenesis. A surprising number of genetic syndromes predispose to the development of renal cell carcinoma, and genes associated with five of these syndromes have been already identified: VHL, MET, FH, BHD and HRPT2. Few cancers have as many different types of genetic predisposition as renal cancer, although to date only a small proportion of renal cell cancers can be explained by genetic predisposition.

Essential role of STAT3 for embryonic stem cell pluripotency

Propagation of mouse embryonic stem (ES) cells in vitro requires exogenous leukemia inhibitory factor (LIF) or related cytokines. Potential downstream effectors of the LIF signal in ES cells include kinases of the Src, Jak, and mitogen-activated protein families and the signal transducer and transcriptional activator STAT3. Activation of nuclear STAT3 and the ability of ES cells to grow as undifferentiated clones were monitored during LIF withdrawal. A correlation was found between levels of STAT3 activity and maintenance of an undifferentiated phenotype at clonal density. In contrast, variation in STAT3 activity did not affect cell proliferation. The requirement for STAT3 was analyzed by targeted mutagenesis in ES cell lines exhibiting different degrees of LIF dependency. An insertional mutation was devised that abrogated Stat3 gene expression but could be reversed by Cre recombination-mediated excision. ES cells heterozygous for the Stat3 mutation could be isolated only from E14 cells, the line least dependent on LIF for self-renewal. Targeted clones isolated from other ES cell lines were invariably trisomic for chromosome 11, which carries the Stat3 locus, and retained normal levels of activated STAT3. Cre-regulated reduction of Stat3 gene copy number in targeted, euploid E14 clones resulted in dose-dependent losses of STAT3 activity and the efficiency of self-renewal without commensurate changes in cell cycle progression. These results demonstrate an essential role for a critical amount of STAT3 in the maintenance of an undifferentiated ES cell phenotype.

Molecular cloning and expression of a chloride channel-associated protein pICln in human young red blood cells: association with actin

We report the cloning and sequencing from human reticulocytes of cDNA coding for the Cl- channel-associated protein, pICln. Human reticulocyte pICln (HRpICln) cDNA encodes a protein (predicted molecular mass 26293Da) identical with human non-pigmented ciliary epithelial cell pICln. By using full-length HRpICln cDNA (approx. 1.2 kb) to probe human lymphocyte metaphase-chromosome spreads, the location of the human ICln gene was mapped to 11q13 by fluorescence in situ hybridization analysis. Polyclonal antibodies to recombinant HRpICln detected bands at approx. 43 kDa and approx. 37 kDa in both normal (AA) and sickle (SS) red blood cell (RBC) ghost membranes. In SS ghosts, and in ghosts from a patient with autoimmune haemolytic anaemia with 9.8% reticulocytes, the amount of HRpICln was increased compared with AA ghosts, suggesting that the expression or membrane assembly of HRpICln is cell age-dependent. Laser scanning confocal fluorescent microscopy immunolocalized HRpICln largely to the RBC membrane. The increased staining intensity of HRpICln in a reticulocyte-enriched AA RBC density-separated fraction is consistent with a dependence of HRpICln membrane content on cell age. HRpICln and beta-actin form stable complexes in vivo, demonstrated with the yeast two-hybrid system. Low-ionic-strength extraction of ghost membranes, which results in the extraction of the spectrin-actin cytoskeleton, also results in the extraction of HRpICln, consistent with the possibility for the association of these proteins in RBCs in vivo. The results presented here establish the presence of the Cl- channel-associated protein, pICln, in human RBCs, and raises the possibility that this protein has a role in RBC Cl- transport and volume regulation in young RBCs. Moreover the association of RBC pICln with actin offers a model in which to test interactions between RBC ion channels and the cytoskeleton.

Ig V region hypermutation in B cell hybrids mimics in vivo mutation and allows for isolation of clonal variants

In order to investigate the regulation of Ig hypermutation, we have established a cell culture system in which reversion of a V region stop codon in a stably transfected Ig gene permits the quantitation of mutation rates by fluctuation analysis. Transfected heavy chain V regions associated with the mu constant region undergo low rates of mutation in the NSO plasmacytoma cell line and a moderate rate of mutation in the 18.81 pre-B cell line. Most of the hybrids created by fusing these two cell lines resembled the non-permissive NSO cell line, though a few hybrids had constitutive V region mutation rates that were even higher than 18.81 and similar to the high rates of mutation that occur in vivo (Green, N. S., Rabinowitz, J. L., Zhu, M., Kobrin, B. J. and Scharff, M. D. (1995) Proc. Nat. Acad. Sci. (USA) 92, 6304 6308). Characterization of these hybrids now demonstrates that the transfected genes were integrated outside of the Ig locus. Mutation was due to multiple single base pair replacements in the V region and not the C region, was ongoing and often arose in hot spot motifs described by V region hypermutation in vivo. Subcloning of unstable hybrids allowed for the isolation of highly related clones with 44-70-fold different mutation rates. These results suggest that V region hypermutation in this mode in vitro systems is under both positive and negative regulation.