Predictive value of sperm-FISH analysis on the outcome of preimplantation genetic diagnosis (PGD) for a pericentric inversion inv5(p15.3q11.2) carrier

Pericentric inversion of chromosome 6 and male fertility problems

As a significant chromosomal structural abnormality, chromosomal inversion is closely related to male infertility. For inversion carriers, the interchromosomal effect explains male infertility, but its specific mechanism remains unclear. Additionally, inversion carriers with different chromosomes have different clinical manifestations. Therefore, genetic counseling is difficult in clinical practice. Herein, four male carriers of pericentric inversion in chromosome 6 have been described. Two patients showed asthenospermia, one showed azoospermia, and the wife of the remaining patient had recurrent miscarriages. Through a literature search, the association between the breakpoint of pericentric inversion in chromosome 6 and male fertility problems are also discussed in this study. Overall, important genes related to asthenospermia in chromosome 6p21 were found, which may be related to the clinical phenotype. These results suggest that physicians should focus on the breakpoints of inversion in genetic counseling.

Criteria to evaluate patterns of segmental and complete aneuploidies in preimplantation genetic testing for aneuploidy results suggestive of an inherited balanced translocation or inversion

Objective

To define criteria for determining when preimplantation genetic testing for aneuploidy (PGT-A) results are suggestive of a potential balanced chromosomal rearrangement in the egg or sperm source and warrant karyotyping.

Design

Performance evaluation of criteria developed to assess PGT-A results for patterns of imbalances suggestive of a balanced chromosomal rearrangement in the egg or sperm source.

Setting

A single PGT-A laboratory and multiple in vitro fertilization centers.

Patients

Reproductive couples who underwent routine PGT-A testing.

Interventions

Karyotyping of reproductive couples for whom patterns of imbalances observed in PGT-A results suggested a balanced chromosomal rearrangement in the egg or sperm source.

Main Outcome Measures

Correct or incorrect flagging of predicted translocation in either the egg or sperm source based on chromosome analysis.

Results

Proposed criteria correctly predicted a balanced reciprocal translocation in 97% of cases (n = 33), a (13;14) Robertsonian translocation in all cases (n = 3), and an inversion in all cases (n = 2). Other criteria evaluated were determined to be ineffective because of relatively low occurrences that met the criteria and/or low predictive value.

Conclusions

Our results showed that the proposed criteria were effective for evaluating patterns of imbalances observed in PGT-A results suggestive of a potential chromosomal rearrangement in the egg or sperm source. Our proposed criteria can be employed by clinicians in the in vitro fertilization setting in combination with a patient's reproductive history to identify PGT-A patients who are likely carriers of balanced chromosomal rearrangements.

Fertility problems in males carrying an inversion of chromosome 10

Chromosomal inversion is closely related to male infertility. Inversion carriers may produce abnormal gametes, which may lead to partial duplication/deletion of the embryonic chromosome and result in spontaneous abortion, a fetus with multiple anomalies, or birth of a malformed child. Genetic counselling remains challenging for these carriers in clinical practice. We report two male carriers with inversion of chromosome 10 and review 26 reported cases. In the first case, 46,XX,inv(10)(p13q22) of the fetal chromosome was found in prenatal diagnosis; this was inherited from the paternal side with 46XY,inv(10)(p13q22). Another case was a male carrier with inv(10)(q21.2q22.1). There have been 25 (89.3%) cases of pericentric inversion and three (10.7%) cases of paracentric inversion involving chromosome 10. Of 28 cases, nine were associated with pregestational infertility of the couples, while the other 19 cases were associated with gestational infertility of the couples or normozoospermia. The breakpoints at 10p15, 10p11, 10q11, and 10q21 were associated with pregestational infertility of the couples. The breakpoints at 10p15, 10p14, 10p13, 10p12, 10p11, 10q11, 10q21, 10q22, 10q23, 10q24, 10q25, and 10q26 were related to gestational infertility of the couples or normozoospermia. Although there is a high risk of infertility or recurrent miscarriages, carriers with inversion of chromosome 10 might produce healthy offspring. Natural pregnancy can be used as a choice for inversion carriers with recurrent spontaneous abortion.

Chromosomal analysis of blastocysts from balanced chromosomal rearrangement carriers

Balanced chromosomal rearrangements (CRs) are among the most common genetic abnormalities in humans. In the present study, we have investigated the degree of consistency between the chromosomal composition of the blastocyst inner cell mass (ICM) and trophectoderm (TE) in carriers with balanced CR, which has not been previously addressed. As a secondary aim, we have also evaluated the validity of cleavage-stage preimplantation genetic diagnosis (PGD) based on fluorescence in situ hybridization (FISH) of blastocysts from CR carriers. Blastocyst ICM and TE were screened for chromosomal aneuploidy and imbalance of CR-associated chromosomes based on whole-genome copy number variation analysis by low-coverage next-generation sequencing (NGS) following single-cell whole-genome amplification by multiple annealing and looping-based amplification cycling. The NGS results were analyzed without knowledge of cleavage-stage FISH results. NGS results for blastocyst ICM and TE from CR carriers were 86.49% (32/37) consistent. Of the 1702 (37×46) chromosomes examined, 99.47% (1693/1702) showed consistency. However, only 40.0% (18/45) of all embryos had consistent results for chromosomes involved in CR, as determined by blastocyst NGS and cleavage-stage FISH. Of the 85 CR-affected chromosomes analyzed by FISH, 37.65% (32/85) were incongruous with NGS results, with 87.5% (28/32) showing imbalanced composition by FISH but balanced composition by NGS. These results indicate that chromosomal composition of blastocyst ICM and TE in balanced CR carriers is highly consistent, and that PGD based on cleavage-stage FISH is inaccurate; therefore, using blastocyst TE biopsies for NGS-based PGD is recommended for identifying chromosomal imbalance in embryos from balanced CR carriers.

Is the resulting phenotype of an embryo with balanced X-autosome translocation, obtained by means of preimplantation genetic diagnosis, linked to the X inactivation pattern?

OBJECTIVE

To examine if a balanced female embryo with X-autosome translocation could, during its subsequent development, express an abnormal phenotype.

DESIGN

Preimplantation genetic diagnosis (PGD) analysis on two female carriers with maternal inherited X-autosome translocations.

SETTING

Infertility center and genetic laboratory in a public hospital.

PATIENT(S)

Two female patients carriers undergoing PGD for a balanced X-autosome translocations: patient 1 with 46,X,t(X;2)(q27;p15) and patient 2 with 46,X,t(X;22)(q28;q12.3).

INTERVENTION(S)

PGD for balanced X-autosome translocations.

MAIN OUTCOME MEASURE(S)

PGD outcomes, fluorescence in situ hybridization in biopsied embryos and meiotic segregation patterns analysis of embryos providing from X-autosome translocation carriers.

RESULT(S)

Controlled ovarian stimulation facilitated retrieval of a correct number of oocytes. One balanced embryo per patient was transferred and one developed, but the patient miscarried after 6 weeks of amenorrhea. In X-autosome translocation carriers, balanced Y-bearing embryos are most often phenotypically normal and viable. An ambiguous phenotype exists in balanced X-bearing embryos owing to the X inactivation mechanism. In 46,XX embryos issued from an alternate segregation, der(X) may be inactivated and partially spread transcriptional silencing into a translocated autosomal segment. Thus, the structural unbalanced genotype could be turned into a viable functional balanced one. It is relevant that a discontinuous silencing is observed with a partial and unpredictable inactivation of autosomal regions. Consequently, the resulting phenotype remains a mystery and is considered to be at risk of being an abnormal phenotype in the field of PGD.

CONCLUSION(S)

It is necessary to be cautious regarding to PGD management for this type of translocation, particularly in transferred female embryos.

Different segregation patterns in five carriers due to a pericentric inversion of chromosome 1

Pericentric inversion can produce recombinant gametes; however, meiotic segregation studies on the relationship between the frequency of recombinants and the inverted segment size are rare. Triple-color fluorescence in situ hybridization (FISH) was performed to analyze the meiotic behavior in five inv(1) carriers with different breakpoints. Recombination gametes were absent in Patient 1, whereas the percentages of the recombinants in Patients 2, 3, 4, and 5 were of 9.2%, 15.3%, 17.3%, and 40.9%, respectively. A significant difference was present for the frequencies of the recombinant spermatozoa among the five patients (p < 0.001). For each patient, the frequency of the two types of recombinant gametes (dup(1p)/del(1q) or del(1p)/dup(1q)) did not exhibit a significant difference in comparison with the expected 1:1 ratio (p > 0.05). The meiotic segregation of nine inv(1) carriers (including those presented in this paper) is now available. A significant correlation was discovered between the rate of recombination and the proportion of the chromosome implicated in the inversion (R = 0.9435, p < 0.001). The frequency of the recombinant gametes was directly related to the proportion of the chromosome that was inverted. Sperm-FISH allowed an additional comprehension of the patterns of meiotic segregation and provided accurate genetic counseling.

Chromosomal abnormalities in men with pregestational and gestational infertility in northeast China

PURPOSE

To detect incidences and the types of chromosomal abnormalities in Chinese men with infertility and determine chromosomal factors association with various phenotypes.

METHODS

Semen analysis and karyotype analysis by G-banding were carried out in 4,659 idiopathic infertile males; additionally, multiplex PCR using nine specific sequence-tagged sites (STSs) was used to detect azoospermia factor (AZF) microdeletions in 412 patients with Y chromosomal abnormalities.

RESULTS

Male infertility was divided into pregestational infertility, characterized by failure to produce a fertilized ovum, and gestational infertility, characterized by embryo loss after fertilization. The former can result from azoospermia, oligozoospermia or oligoasthenozoospermia syndrome, while the latter is associated with developmental early pregnancy loss, habitual miscarriage and stillbirth. Among 4,659 male patients, 412 (8.84 %) showed abnormal chromosomal karyotypes, including 314 (6.74 %) with sex chromosomal abnormalities and 98 (2.10 %) with autosomal abnormalities. The prevalences of numerical and structural abnormalities among patients with chromosomal abnormalities were 259/412 (62.86 %) and 153/412 (37.14 %), respectively. Furthermore, structural sex chromosomal abnormalities were represented by various phenotypic profiles (46,XX, 47,XYY and 45,X/46,XY), and a prevalence of AZF microdeletions of 19/79 (24.05 %). AZF microdeletions were highly associated with Y chromosomal abnormalities (P = 0.018).

CONCLUSION

Various chromosomal abnormalities that result in male infertility could affect spermatogenesis or embryonic development at different levels. Sex chromosomal and autosomal abnormalities were highly associated with pregestational and gestational infertility, respectively. AZF microdeletions may play an important role in lowering the stability of the Y chromosome.

Analysis using fish of sperm and embryos from two carriers of rare rob(13;21) and rob(15;22) robertsonian translocation undergoing PGD

The majority of fluorescence in situ hybridization (FISH) studies on the meiotic segregation of Robertsonian translocations focus on the most common types, rob(13; 14) and rob(14; 21). Here we report the first study for carriers of rare Robertsonian translocations rob(13; 21) and rob(15; 22) combining analysis of meiotic segregation in sperm and blastomeres following pre-implantation genetic diagnosis (PGD). Dual-colour FISH was applied to nuclei from spermatozoa and blastomeres from PGD embryos using two subterminal contig probes for each translocation, and a second round with probes for chromosomes 16 and 18. Patient 1 had a rob(13; 21) and patient 2 had a rob(15; 22), and 86.3% and 87.5% of gametes respectively were consistent with meiotic segregation resulting in a normal or balanced chromosome complement. Analysis of embryos showed that for patient 1 and 2 respectively, 25% and 46% were balanced, and of the unbalanced embryos, 50% and 31% were mosaic or chaotic. Our patients with a rob(13; 21) and rob(15; 22) were found to have a similar meiotic segregation pattern to that for male carriers of the common Robertsonian translocations. The observed rate in unbalanced embryos being mosaic or chaotic may result in an increased risk of chromosomal abnormalities. Our results may help to improve the genetic counseling for carriers of rare Robertsonian translocations.