Congenital Complex Chromosome rearrangements (CCRs) compatible with life are rare in humans. We report a de novo CCR involving chromosomes 8, 11 and 16 with 4 breakpoints in a patient with mild ...dysmorphic features, acquisition delay and psychotic disorder. Conventional cytogenetic analysis revealed an apparently balanced 8;16 translocation. Further FISH analysis with WCP 8 and WCP 16 probes revealed the presence of a third chromosome involved in the translocation. The multicolour karyotype confirmed the complexity of the rearrangement and showed that the derivative chromosome 8 was composed of 3 distinct segments derived from chromosomes 8, 16 and 11. The breakpoints of this complex rearrangement were located at 8q21, 11q14, 11q23 and 16q12. Comparative genomic hybridization (CGH) and array-CGH were performed to investigate the possibility of any genomic imbalance as a result of the complex rearrangement. No imbalance was detected by these two techniques. Our study showed: i) the necessity to confirm reciprocal translocations with FISH using painting probes, particularly when the karyotype resolution is weak; ii) the usefulness of multicolour karyotype for the characterization of structural chromosomal rearrangements, particularly when they are complex; iii) the usefulness of CGH and array-CGH in cases of abnormal phenotype and apparently balanced rearrangement in order to explore the breakpoints and to detect additional imbalances.
In the adult mammalian cochlea, post-injury hair cell losses are considered to be irreversible. Recent studies in cochlear explants of embryonic rodents show that the organ of Corti can replace lost ...hair cells after injury. We have investigated this topic in vivo during the period of cochlear development. Rat pups were treated with a daily subcutaneous injection of 500 mg/kg amikacin for eight consecutive days between postnatal day 9 (PND 9) and PND 16. During this period the organ of Corti is not fully mature, but hair cells are hyper-sensitive to aminoglycoside antibiotics. Scanning and transmission electron microscopy was used to evaluate morphological changes in the organs of Corti during the treatment and at different post-treatment periods, up until PND 90. A massive loss in outer and inner hair cells was observed at least as early as PND 14. A prominent feature in the apical part of cochleas at PND 21 and 35 was the transient presence of small atypical cells in the region of pre-existing outer hair cells. These atypical cells had tufts of microvilli reminiscent of nascent stereociliary bundles. A second striking observation was the replacement of degenerating inner hair cells by pear-shaped supporting cells throughout the cochlea. These cells were covered with long microvilli, and their basal pole was contacted by both afferent and efferent fibers, as in the early stages of inner hair cell maturation. At PND 55 and 90, these features were not clearly observed due to further cytological changes in the organ of Corti. It is possible that an attempt at hair cell neodifferentiation could occur in vivo after an amikacin treatment in the rat during the period of cochlear hyper-sensitivity to antibiotic.
Recent studies have shown that an attempt at auditory hair cell neodifferentiation occurs in vivo in the rat organ of Corti after amikacin intoxication during the last stages of cochlear maturation. ...Atypical cells, with morphological characteristics reminiscent of very immature sensory hair cells, were transiently observed after outer hair cell losses. The aim of the present study was to assess (i) if this attempt at hair cell neodifferentiation was related to the degree of maturity of the organ of Corti and (ii) to characterise morphological and molecular changes in the scarring epithelium. We therefore investigated, using electron and confocal microscopy, morphological and molecular changes in cochleae from rats treated with amikacin at two different periods: from post natal day (PND) 1 to PND 8, when the organ of Corti is very immature; and from PND 30 to 37, when the organ of Corti is morphologically and functionally mature. In both groups, transient atypical cells were observed, attesting that the attempt at hair cell neodifferentiation is not strictly related to the immaturity of the cochlea. The results also suggest that Deiters cells are involved in the appearance of atypical cells, possibly through a transdifferentiation process. Finally, it appears that non-sensory epithelial cells from the outer spiral sulcus progressively colonize the region of pre-existing outer hair cells.
Benign and malignant thyroid tumors constitute a wide range of neoplasias showing recurrent chromosome abnormalities. Cytogenetic studies of thyroid hyperplasias and follicular adenomas revealed ...hyperdiplo d karyotypes with a characteristic sequence of trisomies (7, 5, 12, 14, 16, 17, 20 and 22) starting with trisomy 7. Comparative genomic hybridization (CGH) findings on thyroid oncocytic tumors showed similar chromosomal gains with no difference observed between adenomas and carcinomas. Follicular thyroid carcinomas exhibit losses of 3p25-pter predominantly or of 22,13 and 1p segments. Formation of fusion genes PAX8 - PPARgamma1 caused by a t(2;3)(q13;p25) has been observed in several cases of follicular carcinomas only. Loss of chromosome 22 has been found most frequently associated with widely invasive follicular carcinomas. Activation of the RET protooncogene through chromosome rearrangements involving subband 10q11.2 represent the most common and specific genetic alteration in papillary thyroid carcinoma. Several chimeric genes resulting in the fusion of the tyrosine kinase domain of RET with the 5' sequences of different genes have been described. Germline mutations in RET are associated with medullary thyroid carcinoma in multiple endocrine neoplasia type 2 (MEN2). Cytogenetics of thyroid tumors, using conventional and molecular methods (FISH, CGH) demonstrated that particular chromosome aberrations may be related to the clinical behavior of these tumors and may provide informations for their diagnosis or prognosis.
Since the establishment of human karyotype in 1956, human cytogenetic has quickly progressed. The description of the Philadelphia chromosome in 1960 led up to new applications of cytogenetic in the ...fields of hematology and oncology. The initial techniques allowed only uniform staining of chromosomes, limiting the detection of most structural rearrangements. Many approaches aimed to gain a better knowledge of chromosomal structure, a better understanding of rearrangements, and a better identification of the chromosomes were developed: autoradiography, banding techniques, electronic microscopy. Since 1980, new developments in clinical cytogenetic and molecular biology have occurred. In situ labeling using non-radioactive probes onto chromosomes and nuclei was developed: fluorescence in situ hybridization (Fish) was born. Fish allows detecting many chromosomal abnormalities of number and/or structure. The major limitation of this technique is that its use should be based on known indications for the choice of the probe. Multicolor karyotype (M-Fish or Sky), the most recent development of Fish on metaphase spreads, allows to overcome this limit. As shown here in three examples, M-Fish allows to describe precisely complex rearrangements in hematological malignancies and solid tumors. Finally, if no metaphase is available, comparative genomic hybridization (CGH) can be performed to detect and simultaneously localize on chromosomes gains or losses in genomic DNA.
Several lines of evidence indicate a crucial role for unconventional myosins in the function of the sensory hair cells of the inner ear. We report here the characterization of the cDNAs encoding two ...unconventional type I myosins from a mouse cochlear cDNA library. The first cDNA encodes a putative protein named Myo1c, which is likely to be the murine orthologue of the bullfrog myosin Iβ and which may be involved in the gating of the mechanotransduction channel of the sensory hair cells. This myosin belongs to the group of short-tailed myosins I, with its tail ending shortly after a polybasic, TH-1-like domain. The second cDNA encodes a novel type I myosin Myo1f which displays three regions: a head domain with the conserved ATP- and actin-binding sites, a neck domain with a single IQ motif, and a tail domain with the tripartite structure initially described in protozoan myosins I. The tail of Myo1f includes (1) a TH-1 region rich in basic residues, which may interact with anionic membrane phospholipids; (2) a TH-2 proline-rich region, expected to contain an ATP-insensitive actin-binding site; and (3) a SH-3 domain found in a variety of cytoskeletal and signaling proteins. Northern blot analysis indicated that the genes encoding Myo1c and Myo1f display a widespread tissue expression in the adult mouse.Myo1candMyo1fwere mapped byin situhybridization to the chromosomal regions 11D-11E and 17B-17C, respectively. The human orthologuous genesMYO1CandMYO1Fwere also characterized, and mapped to the human chromosomal regions 17p13 and 19p13.2–19p13.3, respectively.
Hair cell loss and a non-functional epithelial reorganization appeared in the organ of Corti after acoustic or toxic damage. Moreover, in the drug damaged organ of Corti, transient atypical cells ...were recently described with characteristics of both immature hair cells and/or non-sensory epithelial cells. The phenotype of these atypical cells has been now investigated by using the galectine 1 (GAL-1) antibody. In the normal organ of Corti, this antibody recognizes all the epithelial cells except the sensory hair cells and their supporting cells. At PD 21, transient atypical cells were not stained by GAL-1 antibody, suggesting that they were originated from hair cells or their supporting cells. Later, the organ of Corti was substituted by an epithelial scare, GAL-1 stained. This study also emphasizes the particular resistance of the cochlear apex to degeneration after antibiotic intoxication.
In the organ of Corti, outer hair cells (OHCs) are sensory effectors responsible for the high sensitivity and sharp tuning of the cochlea. Whilst the distribution and organization of actin and ...tubulin in adult OHCs have been extensively studied, less is known about developing OHCs. In this study we use a quantitative cytometric approach on rat isolated OHCs to measure the distribution of these cytoskeletal proteins from the first stages of development (postnatal day 5) to the adult stage. We report a general decrease in both actin and tubulin concentrations during OHC maturation. Actin first decreases in the apical domain, and then in the medio-basal domain. In the apical domain, this could be related to the physiological reduction in the number of stereocilia occurring during ciliogenesis. In the medio-basal domain, the decrease, accompanied by a redistribution of actin toward the lateral wall, is possibly related to the general reorganization of cytoplasmic organelles, to the maturation of the cortical lattice, and to cell growth. Tubulin concentration decreases regularly in both the apical and the medio-basal domains. This developmental change in tubulin concentration could be due to the regression of the kinocilium that occurs by the end of ciliogenesis, and, as argued for actin, to the general reorganization of cytoplasmic organelles, and to cell growth.
Immature outer hair cells (OHCs), isolated from developing rat cochlea without using proteolytic enzymes, were maintained in short-term culture in a clot of coagulated plasma. Cell viability was ...assessed by a laser scanning image cytomer, using double-fluorescent labeling. Light and transmission electron microscopy was used to study the morphology of isolated cells. Ten to 60 healthy OHCs were obtained from one cochlea, either as single isolated cells or clusters containing 2–10 cells from the same row. Although dead cells were observed only 1 h after dissociation, there were still viable cells after 6 h. Isolated OHCs were not perfectly cylindrical, due to the immaturity of their cortical structures. One hour after dissociation the ultrastructural organization of the isolated cells was generally well preserved, but this was followed by dilatation of the Golgi apparatus and endoplasmic reticulum. Specific changes in isolated OHCs were also observed at the subsurface cisternae and cuticular plate. Although degenerating OHCs generally showed a classic pattern of necrosis, certain morphological features reminiscent of apoptosis were also observed. This study emphasises the difficulty involved in investigating isolated immature OHCs in vitro and provides a basis for future research into the physiological requirements of isolated immature OHCs.
