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.

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.

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.

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.

Live Birth Rates in Women Under 38 Years Old with AMH Level < 1.2 ng/ml in the First In Vitro Fertilization + / - Intracytoplasmic Sperm Injection: Retrospective Study and Arguments for Care.

Many studies failed to show a predictive impact of AMH levels on the chances of pregnancy; however, acceptable pregnancy rates for young women with low AMH levels were observed in IVF + / - ICSI. The objectives of this retrospective study were to evaluate the clinical pregnancy and live birth rates in the first IVF + / - ICSI cycle in women under 38 years old with AMH level < 1.2 ng/ml and to determine the arguments for care. We classified the women into three groups: group A: AMH < 0.4 ng/ml (n: 86); group B: AMH: 0.4 to 0.8 ng/ml (n: 90); and group C: AMH > 0.8 to < 1.2 ng/ml (n: 92). We recorded data on the patients' characteristics, stimulation cycles, embryo cultures, and ongoing pregnancies. No difference was observed between the three groups for the number of embryos transferred, the clinical pregnancy, and the live birth rates (LBR) per embryo transfer (LBR/transfer: 24.1% in group A, 25.9% in group B, and 28.1% in group C). The young age of the women reassures about the oocyte quality, but a low level of AMH may raise concerns about a lower quantitative oocyte yield, leading to accelerated management of the couple in IVF + / - ICSI.

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.

Characterization of a novel strain of Aspergillus aculeatinus: From rhamnogalacturonan type I pectin degradation to improvement of fruit juice filtration.

Aspergillus spp. are well-known producers of pectinases commonly used in the industry. Aspergillus aculeatinus is a recently identified species but poorly characterized. This study aimed at giving a comprehensive characterization of the enzymatic potential of the O822 strain to produce Rhamnogalacturonan type I (RGI)-degrading enzymes. Proteomic analysis identified cell wall degrading enzymes (cellulases, hemicellulases, and pectinases) that accounted for 92 % of total secreted proteins. Twelve out of fifty proteins were identified as RGI-degrading enzymes. NMR and enzymatic assays revealed high levels of arabinofuranosidase, arabinanase, galactanase, rhamnogalacturonan hydrolases and rhamnogalacturonan acetylesterase activities in aqueous extracts. Viscosity assays carried out with RGI-rich camelina mucilage confirmed the efficiency of enzymes secreted by O822 to hydrolyze RGI, by decreasing viscosity by 70 %. Apple juice trials carried out at laboratory and pilot scale showed an increase in filtration flow rate and yield, paving the way for an industrial use of enzymes derived from A. aculeatinus.

Three novel rhamnogalacturonan I- pectins degrading enzymes from Aspergillus aculeatinus: Biochemical characterization and application potential.

Rhamnogalaturonans I (RGI) pectins, which are a major component of the plant primary cell wall, can be recalcitrant to digestion by commercial enzymatic cocktails, in particular during fruit juice clarification process. To overcome these problems and get better insights into RGI degradation, three RGI degrading enzymes (RHG: Endo-rhamnogalacturonase; ABF: α-Arabinofuranosidases; GAN: Endo-ß-1,4-galactanase) from Aspergillus aculeatinus were expressed in Pichia pastoris, purified and fully biochemically characterized. All three enzymes showed acidic pH optimum, and temperature optima between 40-50 °C. The Km values were 0.5 mg.ml-1, 1.64 mg.ml-1 and 3.72 mg.ml-1 for RHG, ABF, GAN, respectively. NMR analysis confirmed an endo-acting mode of action for RHG and GAN, and exo-acting mode for ABF. The application potential of these enzymes was assessed by measuring changes in viscosity of RGI-rich camelina mucilage, showing that RHG-GAN enzymes induced a decrease in viscosity by altering the structures of the RGI backbone and sidechains.

Autologous and allogeneic HLA KIR ligand environments and activating KIR control KIR NK-cell functions.

NK-cell function is regulated by a balance between inhibitory and activating killer cell immunoglobulin-like receptors (KIR) that specifically recognize HLA class I molecules. Using KIR-specific mAb to discriminate between KIR2DS1 and KIR2DL1 receptors, we show that KIR2DS1(+) NK cells are C2-alloreactive only from C2(-) individuals. Moreover, using an in vitro model of NK-cell expansion, we show here that the frequency of KIR2DL1(+) NK cells is significantly higher in the absence of C2 ligand on stimulator EBV-B cells than in its presence. This observation was made regardless of the presence or absence of the autologous C2 ligand, suggesting that the C2(-) EBV-B stimulator cells used in this in vitro model could activate unlicensed KIR2DL1(+) NK cells. In the case of KIR2DL1(+)/S1(+) genotyped individuals, KIR2DS1(+) NK-cell frequency was increased after stimulation with C2(+) compared with C2(-) stimulator B cells, but only from C2(-) individuals. Altogether, these data highlight the C2 alloreactivity of KIR2DS1(+) NK cells that is only observed in C2(-) individuals. These results provide new insights into the way in which NK KIR cell expansion might be regulated in an allogeneic environment.

Meiotic segregation of X-autosome translocation in two carriers and implications for assisted reproduction.

The aim of this study was to analyse and compare the meiotic segregation of X-autosome translocation in two male carriers and to discuss couple-specific treatment modality before intracytoplasmic sperm injection (ICSI). Meiotic segregation was analysed by fluorescence in-situ hybridization (FISH) in spermatozoa of two men who were carriers of a X-autosome translocation: 46,Y,t(X;2)(p21;p25.3) (patient 1) and 46,Y,t(X;18)(qll;pl1.1) (patient 2). The results indicated a majority of unbalanced spermatozoa (62.05%) for patient 1, but normal or balanced spermatozoa (54.36%) for patient 2. Moreover, the unbalanced gametes resulted from adjacent I, adjacent II and 3:1 segregation, in decreasing frequencies, for patient 1 but from 3:1, adjacent I, adjacent II segregation for patient 2. The results of the meiotic segregation analysis had different treatment implications for assisted reproduction. Couple 1 were advised against ICSI, due to the results of the meiotic segregation in spermatozoa from patient 1 and the age of his wife. For couple 2, the clinic viewed favourably an attempt with ICSI followed by conventional prenatal diagnosis. A 46,XY child was born without malformations.

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.

Characterization and meiotic segregation of a supernumerary marker chromosome in sperm of infertile males: case report and literature review.

This couple presented with a 4-year history of primary infertility. The male partner was found to have oligoasthenozoospermia. A supernumerary marker chromosome (SMC) was found. Fluorescent in situ hybridization (FISH) analyses showed that the SMC was a heterochromatic dicentric marker derived from chromosome 22. Further FISH procedures showed the rate of unbalanced spermatozoa containing one chromosome 22 and the SMC to be 15.6%. Due to the low risk of fetal chromosomal imbalance linked to the paternal SMC and the risk of miscarriage linked to the amniocentesis, the couple declined prenatal diagnosis. A healthy newborn baby was obtained after ICSI.

Molecular cytogenetic analysis by genomic hybridization to determine the cause of recurrent miscarriage.

OBJECTIVE: To characterize a t(2;6) by array-based comparative genomic hybridization (array-CGH) in a couple with recurrent miscarriage, to analyze the meiotic segregation of the t(2;6), and to discuss couple specific care-taking modality before intracytoplasmic sperm injection. DESIGN: Case report. SETTING: INSERM U613 in Brest, France. PATIENT(S): Couple consulting for infertility. INTERVENTION(S): Array-CGH to characterize a t(2;6) and fluorescence in situ hybridization (FISH) to analyze the meiotic segregation were performed. MAIN OUTCOME MEASURE(S): Array-CGH, FISH with a panel of bacterial artificial chromosome clones and commercial probes. RESULT(S): Analyses from peripheral blood lymphocytes identified a t(2;6)(q35;q24) unbalanced reciprocal translocation with microdeletions on the der(2) and the der(6). FISH on spermatozoa found that the frequency of normal (23,X or 23,Y) or "translocation-deletions" (23,X,der(2),der(6) or 23,Y,der(2),der(6)) spermatozoa was 41.10%. CONCLUSION(S): For our 46,XY,t(2;6)(q35;q24) carrier, more than 50% of the spermatozoa are chromosomally unbalanced. Moreover, FISH does not permit a distinction between normal and "translocation-deletion" phenotypes. So, in the possibility of preimplantation genetic diagnosis, is it necessary to select the normal embryos to the detriment of those translocation-deletions carriers? The pathogenicity of these microdeletions not been proved. Because the family history was oriented toward a variation of genetic equipment without phenotypic consequences, the couple decided not to make a selection between the normal embryos and the translocation-deletion carrier embryos.

DNA fragmentation and meiotic segregation in sperm of carriers of a chromosomal structural abnormality.

OBJECTIVE: To determine the meiotic segregation and DNA fragmentation in spermatozoa of carriers of a chromosomal structural abnormality. DESIGN: Case series. SETTING: University hospital. PATIENT(S): Thirty-seven male carriers of a chromosomal structural abnormality (21 with a balanced reciprocal translocation, 7 with a robertsonian translocation, 9 with a pericentric inversion). INTERVENTION(S): Meiotic segregation was analyzed by the human sperm-hamster oocyte fusion technique or by fluorescent in situ hybridization, and DNA fragmentation was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. MAIN OUTCOME MEASURE(S): Relationships between abnormal sperm parameters, DNA fragmentation, and meiotic mechanisms. RESULT(S): The average rates of chromosomally unbalanced spermatozoa were 55.22%, 14.09%, and 18.43% for reciprocal translocation, robertsonian translocation, and pericentric inversion carriers, respectively. The rates of DNA fragmentation were significantly higher in the whole group of carriers of a chromosomal structural abnormality and in each specific group than in the control group. No correlations between sperm DNA fragmentation and parameters of spermogram, age, or percentage of unbalanced chromosomal gametes were found. CONCLUSION(S): The DNA fragmentation rate depends solely on the presence of a chromosomal structural abnormality, and, therefore, a chromosomal structural abnormality predicts DNA fragmentation. Both meiotic segregation and DNA fragmentation studies should be integrated in the genetic exploration of male carriers of a chromosomal structural abnormality.

Study of aneuploidy in large-headed, multiple-tailed spermatozoa: case report and review of the literature.

OBJECTIVE: To determine the meiotic segregation in large-headed, multiple-tailed spermatozoa. DESIGN: Analysis of sperm nuclei by fluorescence in situ hybridization (FISH). SETTING: University hospital. PATIENT(S): A 34-year-old man with 100% morphologically abnormal spermatozoa. INTERVENTION(S): Dual-color FISH for chromosomes 13 and 21 and triple-color FISH for chromosomes X, Y, and 18 were performed. MAIN OUTCOME MEASURE(S): Aneuploidy rates. RESULT(S): More than 99% of the spermatozoa had abnormal content for chromosomes X, Y, 13, 18, and 21. Diploidy, triploidy, and tetraploidy rates were found to be 18.42%, 6.14%, and 33.99% in triple-color FISH and to be 16.09%, 16.28%, and 38.95% in dual-color FISH. CONCLUSION(S): Our results and those from other investigators show that large-headed, multiple-tailed spermatozoa are associated with a high rate of polyploidy and aneuploidy. Intracytoplasmic sperm injection should not be recommended to those patients, not only because of its low success rate but also because of its high genetic risk.

Differing mechanisms of meiotic segregation in spermatozoa from three carriers of a pericentric inversion of chromosome 8.

OBJECTIVE: To determine the meiotic segregation of a pericentric inversion of chromosome 8 in three carriers. DESIGN: Analysis of sperm nuclei by fluorescence in situ hybridization (FISH). SETTING: University hospital. PATIENT(S): Three males with an inv(8). INTERVENTION(S): Triple FISH with the 8q and 8p subtelomeres and the specific alphoid of chromosome 9 probes. MAIN OUTCOME MEASURE(S): Meiotic segregation differences between carriers. RESULT(S): The frequencies of nonrecombinant gametes were 97%, 60.94%, and 61.03%. The frequencies of recombinant sperm were 1.44%, 37.71%, and 37.70%, whereas the size of the inverted segment represented 31%, 61%, and 80% of the size of the whole chromosome 8. CONCLUSION(S): Many factors seem to influence the production of recombinant chromosomes: the affected chromosome and involved region, location of the breakpoints, or size of the inverted segment. Our results show that the rate of recombination varies principally according to the size of the inverted segment.