NUDT6 and NUDT9, two mitochondrial members of the NUDIX family, have distinct hydrolysis activities.

The 22 members of the NUDIX (NUcleoside DIphosphate linked to another moiety, X) hydrolase superfamily can hydrolyze a variety of phosphorylated molecules including (d)NTPs and their oxidized forms, nucleotide sugars, capped mRNAs and dinucleotide coenzymes such as NADH and FADH. Beside this broad range of enzymatic substrates, the NUDIX proteins can also be found in different cellular compartments, mainly in the nucleus and in the cytosol, but also in the peroxisome and in the mitochondria. Here we studied two members of the family, NUDT6 and NUDT9. We showed that NUDT6 is expressed in human cells and localizes exclusively to mitochondria and we confirmed that NUDT9 has a mitochondrial localization. To elucidate their potential role within this organelle, we investigated the functional consequences at the mitochondrial level of NUDT6- and NUDT9-deficiency and found that the depletion of either of the two proteins results in an increased activity of the respiratory chain and an alteration of the mitochondrial respiratory chain complexes expression. We demonstrated that NUDT6 and NUDT9 have distinct substrate specificity in vitro, which is dependent on the cofactor used. They can both hydrolyze a large range of low molecular weight compounds such as NAD+(H), FAD and ADPR, but NUDT6 is mainly active towards NADH, while NUDT9 displays a higher activity towards ADPR.

Sperm Meiotic Segregation Analysis of Reciprocal Translocations Carriers: We Have Bigger FISH to Fry.

Reciprocal translocation (RT) carriers produce a proportion of unbalanced gametes that expose them to a higher risk of infertility, recurrent miscarriage, and fetus or children with congenital anomalies and developmental delay. To reduce these risks, RT carriers can benefit from prenatal diagnosis (PND) or preimplantation genetic diagnosis (PGD). Sperm fluorescence in situ hybridization (spermFISH) has been used for decades to investigate the sperm meiotic segregation of RT carriers, but a recent report indicates a very low correlation between spermFISH and PGD outcomes, raising the question of the usefulness of spermFISH for these patients. To address this point, we report here the meiotic segregation of 41 RT carriers, the largest cohort reported to date, and conduct a review of the literature to investigate global segregation rates and look for factors that may or may not influence them. We confirm that the involvement of acrocentric chromosomes in the translocation leads to more unbalanced gamete proportions, in contrast to sperm parameters or patient age. In view of the dispersion of balanced sperm rates, we conclude that routine implementation of spermFISH is not beneficial for RT carriers.

Bypassing Mendel's First Law: Transmission Ratio Distortion in Mammals.

Mendel's law of segregation states that the two alleles at a diploid locus should be transmitted equally to the progeny. A genetic segregation distortion, also referred to as transmission ratio distortion (TRD), is a statistically significant deviation from this rule. TRD has been observed in several mammal species and may be due to different biological mechanisms occurring at diverse time points ranging from gamete formation to lethality at post-natal stages. In this review, we describe examples of TRD and their possible mechanisms in mammals based on current knowledge. We first focus on the differences between TRD in male and female gametogenesis in the house mouse, in which some of the most well studied TRD systems have been characterized. We then describe known TRD in other mammals, with a special focus on the farmed species and in the peculiar common shrew species. Finally, we discuss TRD in human diseases. Thus far, to our knowledge, this is the first time that such description is proposed. This review will help better comprehend the processes involved in TRD. A better understanding of these molecular mechanisms will imply a better comprehension of their impact on fertility and on genome evolution. In turn, this should allow for better genetic counseling and lead to better care for human families.

Meiotic Segregation of an Isodicentric Derived from Chromosome 15 in Sperm of a Patient with Mosaic Karyotype: Case Report and Review of the Literature.

Small supernumerary marker chromosomes (sSMCs) are defined as structurally abnormal chromosomes that are difficult to identify by conventional cytogenetic techniques. sSMCs are 3.75 times more common in infertile men than in the general population. This study aimed at characterizing a supernumerary marker chromosome in a nonconsanguineous infertile couple and analyzing its meiotic segregation in sperm by multicolor FISH. The male partner's karyotype was mos 47,XY,+idic(15)(pter→q11.1::q11.1→pter)[6]/46,XY[24].ish idic(15)(NOR+,D15Z3+,SNRPN-,D15Z3+,NOR+). In triple FISH using CEP 15, BAC 15, and BAC 21 probes, 4,227 spermatozoa of the patient were analyzed, and the sSMC was detected in only 0.66% of spermatozoa. In triple FISH employing CEP X, CEP Y, and BAC 18 probes, 2,008 spermatozoa of the patient were analyzed. The frequency of disomic and diploid sperm was not significantly different from control donors. To our knowledge, segregation of an sSMC 15 has been reported in only 9 males with non-mosaic karyotypes. These studies described rates of spermatozoa with sSMC 15 ranging from 6.23% to more than 50%. In this work, we report the first meiotic segregation analysis of a chromosome 15-derived sSMC in spermatozoa of a patient with a mosaic karyotype. The low rate of spermatozoa with sSMC detected is concordant with the low proportion of abnormal cells in our patient's lymphocytes. Moreover, the risk of interference of this sSMC with other chromosomes seems minimal. Genetic counseling was recommended given that the risk of chromosomal imbalance in the fetus linked to paternal sSMC was very low. Finally, a healthy boy was born after a natural pregnancy.

MACS-annexin V cell sorting of semen samples with high TUNEL values decreases the concentration of cells with abnormal chromosomal content: a pilot study.

We question whether, in men with an abnormal rate of sperm DNA fragmentation, the magnetic-activated cell sorting (MACS) could select spermatozoa with lower rates of DNA fragmentation as well as spermatozoa with unbalanced chromosome content. Cryopreserved spermatozoa from six males were separated into nonapoptotic and apoptotic populations. We determined the percentages of spermatozoa with (i) externalization of phosphatidylserine (EPS) by annexin V-Fluorescein isothiocyanate (FITC) labeling, (ii) DNA fragmentation by TdT-mediated-dUTP nick-end labeling (TUNEL), and (iii) numerical abnormalities for chromosomes X, Y, 13, 18, and 21 by fluorescence in situ hybridization (FISH), on the whole ejaculate and selected spermatozoa in the same patient. Compared to the nonapoptotic fraction, the apoptotic fraction statistically showed a higher number of spermatozoa with EPS, with DNA fragmentation, and with numerical chromosomal abnormalities. Compared to the whole ejaculate, we found a significant decrease in the percentage of spermatozoa with EPS and decrease tendencies of the DNA fragmentation rate and the sum of disomy levels in the nonapoptotic fraction. Conversely, we observed statistically significant higher rates of these three parameters in the apoptotic fraction. MACS may help to select spermatozoa with lower rates of DNA fragmentation and unbalanced chromosome content in men with abnormal rates of sperm DNA fragmentation.

Asian Population Is More Prone to Develop High-Risk Myelodysplastic Syndrome, Concordantly with Their Propensity to Exhibit High-Risk Cytogenetic Aberrations.

This study explores the hypothesis that genetic differences related to an ethnic factor may underlie differences in phenotypic expression of myelodysplastic syndrome (MDS). First, to identify clear ethnic differences, we systematically compared the epidemiology, and the clinical, biological and genetic characteristics of MDS between Asian and Western countries over the last 20 years. Asian MDS cases show a 2- to 4-fold lower incidence and a 10-year younger age of onset compared to the Western cases. A higher proportion of Western MDS patients fall into the very low- and low-risk categories while the intermediate, high and very high-risk groups are more represented in Asian MDS patients according to the Revised International Prognostic Scoring System. Next, we investigated whether differences in prognostic risk scores could find their origin in differential cytogenetic profiles. We found that 5q deletion (del(5q)) aberrations and mutations in TET2, SF3B1, SRSF2 and IDH1/2 are more frequently reported in Western MDS patients while trisomy 8, del(20q), U2AF1 and ETV6 mutations are more frequent in Asian MDS patients. Treatment approaches differ between Western and Asian countries owing to the above discrepancies, but the overall survival rate within each prognostic group is similar for Western and Asian MDS patients. Altogether, our study highlights greater risk MDS in Asians supported by their cytogenetic profile.

Acute myeloid leukaemia (FAB AML-M4Eo) with cryptic insertion of cbfb resulting in cbfb-Myh11 fusion.

Inv(16)(p13q22) and t(16;16)(p13;q22) are cytogenetic hallmarks of acute myelomonoblastic leukaemia, most of them associated with abnormal bone marrow eosinophils [acute myeloid leukaemia French-American-British classification M4 with eosinophilia (FAB AML-M4Eo)] and a relatively favourable clinical course. They generate a 5'CBFB-3'MYH11 fusion gene. However, in a few cases, although RT-PCR identified a CBFB-MYH11 transcript, normal karyotype and/or fluorescent in situ hybridization (FISH) analyses using commercially available probes are found. We identified a 32-year-old woman with AML-M4Eo and normal karyotype and FISH results. Using two libraries of Bacterial Artificial Chromosome clones on 16p13 and 16q22, FISH analyses identified an insertion of 16q22 material in band 16p13, generating a CBFB-MYH11 type A transcript. Although very rare, insertions should be searched for in patients with discordant cytological and cytogenetic features because of the therapeutic consequences. Copyright © 2015 John Wiley & Sons, Ltd.

Selective mitochondrial DNA degradation following double-strand breaks.

Mitochondrial DNA (mtDNA) can undergo double-strand breaks (DSBs), caused by defective replication, or by various endogenous or exogenous sources, such as reactive oxygen species, chemotherapeutic agents or ionizing radiations. MtDNA encodes for proteins involved in ATP production, and maintenance of genome integrity following DSBs is thus of crucial importance. However, the mechanisms involved in mtDNA maintenance after DSBs remain unknown. In this study, we investigated the consequences of the production of mtDNA DSBs using a human inducible cell system expressing the restriction enzyme PstI targeted to mitochondria. Using this system, we could not find any support for DSB repair of mtDNA. Instead we observed a loss of the damaged mtDNA molecules and a severe decrease in mtDNA content. We demonstrate that none of the known mitochondrial nucleases are involved in the mtDNA degradation and that the DNA loss is not due to autophagy, mitophagy or apoptosis. Our study suggests that a still uncharacterized pathway for the targeted degradation of damaged mtDNA in a mitophagy/autophagy-independent manner is present in mitochondria, and might provide the main mechanism used by the cells to deal with DSBs.

DNA maintenance following bleomycin-induced strand breaks does not require poly(ADP-ribosyl)ation activation in Drosophila S2 cells.

BACKGROUND: Poly-ADP ribosylation (PARylation) is a post translational modification, catalyzed by Poly(ADP-ribose)polymerase (PARP) family. In Drosophila, PARP-I (human PARP-1 ortholog) is considered to be the only enzymatically active isoform. PARylation is involved in various cellular processes such as DNA repair in case of base excision and strand-breaks. OBSERVATIONS: Strand-breaks (SSB and DSB) are detrimental to cell viability and, in Drosophila, that has a unique PARP family organization, little is known on PARP involvement in the control of strand-breaks repair process. In our study, strands-breaks (SSB and DSB) are chemically induced in S2 Drosophila cells using bleomycin. These breaks are efficiently repaired in S2 cells. During the bleomycin treatment, changes in PARylation levels are only detectable in a few cells, and an increase in PARP-I and PARP-II mRNAs is only observed during the recovery period. These results differ strongly from those obtained with Human cells, where PARylation is strongly activating when DNA breaks are generated. Finally, in PARP knock-down cells, DNA stability is altered but no change in strand-breaks repair can be observed. CONCLUSIONS: PARP responses in DNA strands-breaks context are functional in Drosophila model as demonstrated by PARP-I and PARP-II mRNA increases. However, no modification of the global PARylation profile is observed during strand-breaks generation, only changes at cellular levels are detectable. Taking together, these results demonstrate that PARylation process in Drosophila is tightly regulated in the context of strands-breaks repair and that PARP is essential during the maintenance of DNA integrity but dispensable in the DNA repair process.

Immunoglobulin gene translocations in chronic lymphocytic leukemia: A report of 35 patients and review of the literature.

Chronic lymphocytic leukemia (CLL) represents the most common hematological malignancy in Western countries, with a highly heterogeneous clinical course and prognosis. Translocations involving the immunoglobulin (IG) genes are regularly identified. From 2000 to 2014, we identified an IG gene translocation in 18 of the 396 patients investigated at diagnosis (4.6%) and in 17 of the 275 analyzed during follow-up (6.2%). A total of 4 patients in whom the IG translocation was identified at follow-up did not carry the translocation at diagnosis. The IG heavy locus (IGH) was involved in 27 translocations (77.1%), the IG κ locus (IGK) in 1 (2.9%) and the IG λ locus (IGL) in 7 (20.0%). The chromosome band partners of the IG translocations were 18q21 in 16 cases (45.7%), 11q13 and 19q13 in 4 cases each (11.4% each), 8q24 in 3 cases (8.6%), 7q21 in 2 cases (5.7%), whereas 6 other bands were involved once (2.9% each). At present, 35 partner chromosomal bands have been described, but the partner gene has solely been identified in 10 translocations. CLL associated with IG gene translocations is characterized by atypical cell morphology, including plasmacytoid characteristics, and the propensity of being enriched in prolymphocytes. The IG heavy chain variable region (IGHV) mutational status varies between translocations, those with unmutated IGHV presumably involving cells at an earlier stage of B-cell lineage. All the partner genes thus far identified are involved in the control of cell proliferation and/or apoptosis. The translocated partner gene becomes transcriptionally deregulated as a consequence of its transposition into the IG locus. With the exception of t(14;18)(q32;q21) and its variants, prognosis appears to be poor for the other translocations. Therefore, searching for translocations involving not only IGH, but also IGL and IGK, by banding and molecular cytogenetics is required. Furthermore, it is important to identify the partner gene to ensure the patients receive the optimal treatment.

3q26/EVI1 rearrangements in myeloid hemopathies: a cytogenetic review.

The EVI1 gene, located in chromosomal band 3q26, is a transcription factor that has stem cell-specific expression pattern and is essential for the regulation of self-renewal of hematopoietic stem cells. It is now recognized as one of the dominant oncogenes associated with myeloid leukemia. EVI1 overexpression is associated with minimal to no response to chemotherapy and poor clinical outcome. Several chromosomal rearrangements involving band 3q26 are known to induce EVI1 overexpression. They are mainly found in acute myeloid leukemia and blastic phase of Philadelphia chromosome-positive chronic myeloid leukemia, more rarely in myelodysplastic syndromes. They include inv(3)(q21q26), t(3;3)(q21;q26), t(3;21)(q26;q22), t(3;12)(q26;p13) and t(2;3)(p15-23;q26). However, many other chromosomal rearrangements involving 3q26/EVI1 have been identified. The precise molecular event has not been elucidated in the majority of these chromosomal abnormalities and most gene partners remain unknown.

Genetic aspects of monomorphic teratozoospermia: a review.

Teratozoospermia is characterized by the presence of spermatozoa with abnormal morphology over 85 % in sperm. When all the spermatozoa display a unique abnormality, teratozoospermia is said to be monomorphic. Two forms of monomorphic teratozoospermia, representing less than 1 % of male infertility, are recognized: macrozoospermia (also called macrocephalic sperm head syndrome) and globozoospermia (also called round-headed sperm syndrome). Macrozoospermia is defined as the presence of a very high percentage of spermatozoa with enlarged head and multiple flagella. Meiotic segregation studies in 30 males revealed that over 90 % of spermatozoa were aneuploid, mainly diploid. Sperm DNA fragmentation studies performed in a few patients showed an increase in DNA fragmentation index compared to fertile men. Four mutations in the AURKC gene, a key player in meiosis and more particularly in spermatogenesis, have been found to be responsible for macrozoospermia. Globozoospermia is characterized by round-headed spermatozoa with an absent acrosome, an aberrant nuclear membrane and midpiece defects. The rate of aneuploidy of various chromosomes in spermatozoa from 26 globozoospermic men was slightly increased compared to fertile men. However, this increase was of the same order as that commonly found in infertile men with altered sperm parameters. The majority of the studies found that globozoospermic males had a sperm DNA fragmentation index higher than in fertile men. Mutations or deletions in three genes, SPATA16, PICK1 and DPY19L2, have been shown to be responsible for globozoospermia. Identification of the genetic causes of macrozoospermia and globozoospermia should help refine diagnosis and treatment of these patients, avoiding long and painful treatments. Elucidating the molecular causes of these defects is of utmost importance as intracytoplasmic sperm injection (ICSI) is very disappointing in these two pathologies.

A study of aneuploidy and DNA fragmentation in spermatozoa of three men with sex chromosome mosaicism including a 45,X cell line.

Meiotic segregation of mosaic males with a 45,X cell line has been little examined. In this study, we evaluated the risk of aneuploid gametes using fluorescence in situ hybridization (FISH) and DNA fragmentation in ejaculated spermatozoa of three men with sex chromosome mosaicism including a 45,X cell line. Triple- and dual-color FISH were performed. Sperm DNA fragmentation was detected using the TUNEL assay. A significantly increased frequency of XY disomic spermatozoa was observed for patients (P)1 and P2. A significant increase in diploidy and autosomal aneuploidy was found in P2 and P3, respectively. The rate of DNA fragmentation was not different from that observed in a control group. Data from the literature are scarce (only 3 cases reported), making comparison of the present data difficult, especially as the frequencies of the cell lines comprising the mosaicism differed between patients. Furthermore, the proportion of the different cell lines can differ from one tissue to another in the same patient. Whether the relative levels of the several cell lines present in the mosaicism can influence the rate of aneuploid spermatozoa remains unknown.

Breakpoint heterogeneity in (2;3)(p15-23;q26) translocations involving EVI1 in myeloid hemopathies.

Several chromosomal rearrangements involving band 3q26 are known to induce EVI1 overexpression. They include inv(3)(q21q26), t(3;3)(q21;q26), t(3;21)(q26;q22) and t(3;12)(q26;p13). Translocations involving the short arm of chromosome 2 and 3q26 have been reported in more than 50 patients with myeloid disorders. However, although the breakpoints on 2p are scattered over a long segment, their distribution had only been analyzed in 9 patients. We performed fluorescent in situ hybridization with a library of BAC (Bacterial Artificial Chromosome) clones in 4 patients with t(2;3)(p15-23;q26). Our results combined with those of the 9 previously reported patients showed scattering of the breakpoints in 2 regions. A 1.08Mb region in band 2p21 encompassing the MTA3, ZFP36L2 and THADA genes was documented in 5 patients. A second region of 1.83Mb in band 2p16.1 was identified in 8 patients. Four patients showed clustering around the BCL11A gene and the remaining 4 around a long intergenic non-coding RNA, FLJ30838. These regions are characterized by the presence of regulatory sequences (CpG islands and promoters) that could be instrumental in EVI1 overexpression.

MLL partner genes in secondary acute lymphoblastic leukemia: report of a new partner PRRC1 and review of the literature.

Secondary acute lymphoblastic leukemia (sALL) following chemotherapy and/or radiotherapy of previous malignancies represents 2-10% of all cases of ALL. A 72-year-old female patient was diagnosed with acute lymphoblastic leukemia following chemotherapy for a diffuse large B cell lymphoma. Banding cytogenetics showed a t(t(5;11)(q23-31;q23) in 20 of the 21 metaphases examined and fluorescent in situ hybridization confirmed rearrangement of MLL. Long distance inverse-polymerase chain reaction revealed an in-frame fusion between 5'MLL and 3'PRRC1. Sixty-five cases of sALL associated with 11q23/MLL rearrangement, including 47 with a t(4;11)(q21;q23), were retrieved from the literature. Drug regimen used to treat the primary neoplasm was available for 54 patients; 52 had received a topoisomerase II inhibitor, known to induce MLL rearrangement.

Translocation t(2;7)(p11;q21) associated with the CDK6/IGK rearrangement is a rare but recurrent abnormality in B-cell lymphoproliferative malignancies.

Structural abnormalities of chromosome 7q have been regularly reported in chronic B-cell lymphoproliferative disorders. They include chromosomal translocations involving 7q21, leading to overexpression of the CDK6 gene. Three different translocations, t(7;14)(q21;q32), t(7;22)(q21;q11), and t(2;7)(p11;q21), leading to the juxtaposition of the CDK6 gene with a immunoglobulin gene enhancer during B-cell differentiation, have been described. In the past 2 years, we identified three patients with lymphoproliferative malignancy associated with a t(2;7)(p11;q21). Fluorescent in situ hybridization using an IGK probe and a library of bacterial artificial chromosome (BAC) clones located in bands 7q21.2 and 7q21.3, containing CDK6, revealed that the telomeric part of the IGK probe was translocated on the der(7) within a 51-kb region upstream of the transcriptional start site of CDK6. A total of 23 patients with indolent B-cell lymphoproliferative disorders and juxtaposition of the IG and CDK6 genes, including 20 with IGK and CDK6 juxtaposition, have been reported thus far. This rearrangement leads to the overexpression of CDK6, which encodes a cyclin-dependent protein kinase involved in cell cycle G1 phase progression and G1/S transition.