Concomitant MPZ and MFN2 Gene Variants and Charcot Marie Tooth Disease in a Boy: Clinical and Genetic Analysis-Literature Review.

Charcot- Marie- Tooth (CMT) disease includes a group of clinically and genetically heterogeneous neuropathic disorders with an estimated frequency of 1 on 2.500 individuals. CMTs are differently classified according to the age of onset, type of inheritance, and type of inheritance plus clinical features. For these disorders, more than 100 genes have been implicated as causal factors, with mutations in the PMP22 being one of the most common. The demyelinating type (CMT1) affects more than 30% of the CMTs patients and manifests with motor and sensory dysfunctions of the peripheral nervous system mainly starting with slow progressive weakness of the lower extremities. We report here a 12 year- old boy presenting with typical features of CMT1 type, hearing impairment, and inguinal hernia who at the next-generation sequence analysis displayed a concomitant presence of two variants: the c.233 C>T p.Ser 78Leu of the MPZ gene (NM_000530.6) characterized as pathogenetic and the c.1403 G>A p.Arg 468His of the MFN2 gene (NM_014874.3) characterized as VUS. Concomitant variant mutations in CMTs have been uncommonly reported. The role of these gene mutations on the clinical expression and a literature review on this topic is discussed.

Silencing of PNPLA6, the neuropathy target esterase (NTE) codifying gene, alters neurodifferentiation of human embryonal carcinoma stem cells (NT2).

Neuropathy target esterase (NTE) is a protein involved in the development of a polyneuropathy caused by exposure to certain organophosphorus compounds. In vivo and in vitro studies have also associated NTE with embryonic development since NTE null mice embryos are non-viable, and silencing the NTE-codifying gene (Pnpla6) in mouse embryonic stem cells strongly alters the differentiation of vascular and nervous systems. In this paper, human embryonal carcinoma stem cells human-derived NTera2/D1 (hNT2) are used as an in vitro neurodifferentiation model to determine whether PNPLA6 silencing is able to alter the differentiation process. In control cultures, PNPLA6 mRNA levels increased in parallel with other neuroectodermal markers during neurodifferentiation. PNPLA6 silencing with specific interference RNA reached a 97% decrease in gene expression 3days after transfection and with a maximum reduction in NTE enzymatic activity (50%), observed on day 4. Silencing PNPLA6 showed an 80% decrease in quantifiable neuronal cells after 13days in vitro (DIV) compared to controls and absence of different neuronal markers after 66DIV. Microarray data analysis of the PNPLA6-silenced cells showed alterations in several developmental processes, mainly neurogenesis and epithelium tube morphogenesis. PNPLA6 silencing also led to a reduction in electrical activity and an altered neuronal phenotype. This work is the first proof supporting the hypothesis that NTE plays a role in human early neurodevelopment using a human cell differentiation model.

Mitochondrial function, apoptosis and cell cycle delay in the WEHI-3B leukaemia cell line and its variant Ciprofloxacin-resistant WEHI-3B/CPX.

OBJECTIVE: The susceptibility of two cell lines, WEHI-3B myelomonocytic leukaemia and its variant Ciprofloxacin-resistant WEHI-3B/CPX to undergo apoptosis induced by Ciprofloxacin was studied and compared. MATERIALS AND METHODS: Apoptosis was checked by measuring the DNA fragmentation and determining the ratio of apoptotic/necrotic cells. The relationship between the induction of apoptosis and G(1), S or G(2) block in the cell cycle has also been investigated and cytogenetical evaluation of chromosomal aberrations in both cell lines has been carried out. The regulation of expression of Bax and Bcl-2 was also checked by western blotting after Ciprofloxacin treatment. RESULTS: We observed that the resistance of the subline was caused by a small percentage of cells that underwent apoptosis during continuous exposure to Ciprofloxacin in comparison with the parental cell line, whereas the percentage of necrotic cells remained unchanged. The WEHI-3B cells showed a G(2) block and a higher degree of cytogenetic damage after drug exposure. The two cell lines expressed the same level of Bax and Bcl-2 following stimulation by Ciprofloxacin. Only in the resistant subclone, the ratio Bcl-2/Bax reversed in the anti-apoptotic gene expression. CONCLUSION: The resistance to ciprofloxacin observed is not related to mitochondrial function and although Bcl-2/Bax ratio behaviour does not fully explain the resistance of the WEHI3B/CPX subclone it is consistent with phenotypic character of resistance to CPX. The toxic effect on sensitive cells could be mediated by the cell cycle arrest whereas in the resistant clone, the prolonged G(2) phase could play a key role to favour cell cycle progression and proliferation.

Establishment and characterization of new mammary adenocarcinoma cell lines derived from double transgenic mice expressing GFP and neu oncogene.

A new murine cell line, named GFPneu, was established from a mammary adenocarcinoma arising in double transgenic MMTVneu x CMV-GFP mice. Breast tumours develop in 100% of females after 2 months latency, as a result of the over-expression of the activated rat neu oncogene in the mammary glands. All tissues, and in particular the breast tumours, express the GFP protein. This cell line was tumorigenic when inoculated into nude mice and the derived tumours showed the same histological features as the primaries from which they were isolated. Their histopathology reproduces many characteristics of human breast adenocarcinomas, in particular their ability to metastasize. The GFP marker allows us to visualize the presence of lung metastases in fresh tissues immediately, to confirm the histopathology. From a lung metastatic fluorescent nodule, we derived a further cell line, named MTP-GFP, which we also characterized. These two cell lines could be useful to study the role played by the neu oncogene in the maintenance of the transformed phenotype, in the metastatic process, to test novel therapeutic strategies to inhibit primary tumour growth and to observe the generation of distant metastases.

Induction of apoptosis and inhibition of telomerase activity in human bone marrow and HL-60 p53 null cells treated with anti-cancer drugs.

Telomerase plays a key role in the maintenance of chromosomal stability in tumours, and the ability of anti-cancer agents to inhibit telomerase activity is under investigation. In this study, we evaluated the effect of etoposide and taxol, on the telomerase activity and telomere length in human leukaemia p53 null cells and human bone marrow cells, as well as apoptosis and cell cycle modulation. Results showed that after exposure to the drugs, HL-60 cells as well as the human progenitors underwent a block in G2 and subsequently apoptosis, whereas stromal cells from bone marrow did not undergo a block in G2 or enter apoptosis after etoposide exposure. Telomere length increased in stromal cells after treatment with both etoposide and taxol whereas in HL-60 cells only after etoposide treatment with. Bax, bcl-2 and bcl-x change their expression in stromal cells, whereas bcl-x was induced after drug treatment and bcl-2 down regulated in progenitor cells. Our data suggest that telomerase activity and apoptosis are correlated and they seem to be modulated by a common gene, bcl-2.

Refinement of the colony-forming unit-megakaryocyte (CFU-MK) assay for its application to pharmaco-toxicological testing.

In vitro colony-forming unit (CFU) assays can be used in the evaluation of potentially haematotoxic compounds during preclinical testing. The use of undifferentiated haematopoietic cells, able to proliferate and commit towards a specific blood cell lineage, enable selective toxicity to be detected. We optimized the colony-forming unit-megakaryocyte (CFU-MK) assay for toxicological applications. We used a collagen-based colony-forming assay to examine the sensitivity of four cell types: mononuclear human cord blood cells (CBC), mononuclear human bone marrow cells (BMC), cord blood enriched CD34+CD38- cells, and bone marrow enriched CD34+CD38- cells, to the toxic effects of five drugs known to cause thrombocytopenia in humans. The enrichment of CD34+CD38- cells was achieved by using a negative cell separation technique. Our results showed that a comparable toxicity was detected both with CBC, BMC and CD34+CD38- cells enriched from cord blood, whereas CD34+CD38- cells from bone marrow were more resistant to some drugs. The assay showed a high reproducibility of the endpoint measured (IC(50)), independently of the cell type used and donor source. The present study demonstrates that the refined CFU-MK assay is reproducible and can be used for in vitro toxicology studies with CBC as well as BMC.

Inhibition of CFU-E/BFU-E by 3'-azido-3'-deoxythymidine, chlorpropamide, and protoporphirin IX zinc (II): a comparison between direct exposure of progenitor cells and long-term exposure of bone marrow cultures.

Erythropoiesis occurs in two stages: proliferation amplifies cell number, and differentiation stimulates the acquisition of the functional properties of red blood cells. The erythroid colony-forming unit (CFU-E) amplifies the differentiation process in response to erythropoietic stress in vitro, whereas the burst-forming unit (BFU-E), which is not particularly sensitive to erythropoietin stimulation, gives rise to the CFU-E and, when stimulated, produces morphologically-identifiable erythroid colonies. The aim of this work was to evaluate the toxic effects of the antiviral agent, 3'-azido-3'-deoxythymidine (AZT), the antidiabetic drug, chlorpropamide (CLP), and the heme-analogous compound, protophorphirin IX zinc (II) (ZnPP), on the proliferation of erythroblastic progenitors by using human umbilical-cord blood cells and murine progenitors from long-term bone marrow cultures. All these agents may interfere with the hemopoietic process, causing myelotoxicity as an adverse effect via different mechanisms. Our results showed selective toxicity of the three drugs on the erythroid progenitors (IC(50): AZT 0.35 +/- 0.13 microM, ZnPP 23.34 +/- 1.16 microM, CLP 1.07 +/- 0.27 mM), with respect to the myeloid progenitors (IC(50): AZT 0.8 microM, ZnPP 103.9 +/- 3.9 microM and CLP > 2800 microM). The IC(50) values were well correlated with peak plasma levels reached in vivo by the drugs. There was a marked similarity between the drug sensitivities of the human and murine progenitors but differences in toxicity exerted by the drugs on the basis of the time of exposure. Drug treatment of long-term cultures, followed by the clonogenic assay of progenitors collected from them in the absence of the drugs, generally resulted in a lower hematotoxicity.

Establishment and characterization of a new mammary adenocarcinoma cell line derived from MMTV neu transgenic mice.

A new murine cell line, named MG1361, was established from mammary adenocarcinomas arising in a MMTV-neu transgenic mouse lineage where breast tumors develop in 100% of females, due to the overexpression of the activated rat neu oncogene in the mammary gland. The MG1361 cell line shows an epithelial-like morphology, has a poor plating efficiency, low clonogenic capacity, and a doubling time of 23.8 hours. Karyotype and flow cytometry analysis revealed a hypotetraploid number of chromosomes, whereas cell cycle analysis showed 31.2% of cells to be in the G1 phase, 21.4% in S and 47.4% in G2 + M. This cell line maintains a high level of neu expression in vitro. The MG1361 cell line was tumorigenic when inoculated in immunodeficient (nude) mice and the derived tumors showed the same histological features as the primary tumors from which they were isolated. MG1361 cells were positive for specific ER and PgR binding which was competed by tamoxifen, making this cell line useful for the evaluation of endocrine therapy. Moreover, they were sensitive to etoposide treatment, suggesting that they could be a model for the study of chemotherapy-induced apoptosis. As the tumors arising in MMTV-neu transgenic mice have many features in common with human mammary adenocarcinomas (Sacco et al., Gene Therapy 1995; 2: 493-497), this cell line can be utilized to perform basic studies on the role of the neu oncogene in the maintenance of the transformed phenotype, and to test novel protocols of therapeutic strategies.

The use of pre-implantation mouse embryos cultured in vitro in toxicological studies.

The preimplantation mouse embryo has been found to be a good model for various toxicological investigations. This communication deals with two examples of research activities carried out in our laboratory to detect the embryotoxic properties of tritium and of 1,2:3,4-diepoxybutene (DEB). Exposures of blastocysts for 24 hr to concentrations as high as 0.296 kBq/ml tritiated amino acids or nucleoside induced a statistically significant reduction in the percentage of embryos that reached the stage of two-layer inner cell mass (ICM). The same quantity of tritiated arginine, but not of thymidine or tryptophan, also induced a lower percentage of differentiating ICM than the control when added to culture medium during the second cleavage division. These findings support the idea that tritium released by nuclear power plants as HT or as tritiated water (HTO) could become a radiotoxicological problem since it can be converted easily into organic compounds by living organisms. DEB was found to be highly embryotoxic in preimplantation mouse embryos in vitro at micromolar concentrations. This compound is formed in mammalian cells by the oxidative metabolism of 1,3-butadiene, a chemical used in rubber industries and present in tobacco smoke. Again, the most sensitive stages of preimplantation development were found to be the two- and the four-cell embryos. These results were confirmed by in vivo measurements.

Preimplantation embryo sexing by polymerase chain reaction amplification of the sry gene on single mouse blastomeres.

Accurate and rapid sex determination of preimplantation embryos has great potential both in animal breeding and in human pathology. In the past, sex determination has been accomplished by cytogenetic or immunologic means and by polymerase chain reaction amplification of Y-chromosome-specific repetitive sequences. More recently, amplification of the Y-specific single-copy ZFY gene has been used in humans for sex determination of preimplantation embryos. The experiments reported here indicate that another Y-chromosome-specific single-copy gene, the sex-determining region gene (sry) can be successfully amplified from single mouse blastomeres. Blastocysts positive for sry amplification were reimplanted to foster mothers, and six of six newborns were male. We conclude that sry gene amplification can represent a good marker for embryo sex determination.