Biomedical subjects

Sjoerd Repping

Publications and source records attributed to Sjoerd Repping.

23 records · Page 2Linked to original sources

PubMed2002

Recombination between palindromes P5 and P1 on the human Y chromosome causes massive deletions and spermatogenic failure.

It is widely believed that at least three nonoverlapping regions of the human Y chromosome-AZFa, AZFb, and AZFc ("azoospermia factors" a, b, and c)-are essential for normal spermatogenesis. These intervals are defined by interstitial Y-chromosome deletions that impair or extinguish spermatogenesis. Deletion breakpoints, mechanisms, and lengths, as well as inventories of affected genes, have been elucidated for deletions of AZFa and of AZFc but not for deletions of AZFb or of AZFb plus AZFc. We studied three deletions of AZFb and eight deletions of AZFb plus AZFc, as assayed by the STSs defining these intervals. Guided by Y-chromosome sequence, we localized breakpoints precisely and were able to sequence nine of the deletion junctions. Homologous recombination can explain seven of these deletions but not the remaining two. This fact and our discovery of breakpoint hotspots suggest that factors in addition to homology underlie these deletions. The deletions previously thought to define AZFb were found to extend from palindrome P5 to the proximal arm of palindrome P1, 1.5 Mb within AZFc. Thus, they do not define a genomic region separate from AZFc. We also found that the deletions of AZFb plus AZFc, as assayed by standard STSs heretofore available, in fact extend from P5 to the distal arm of P1 and spare distal AZFc. Both classes of deletions are massive: P5/proximal-P1 deletions encompass up to 6.2 Mb and remove 32 genes and transcripts; P5/distal-P1 deletions encompass up to 7.7 Mb and remove 42 genes and transcripts. To our knowledge, these are the largest of all human interstitial deletions for which deletion junctions and complete intervening sequence are available. The restriction of the associated phenotype to spermatogenic failure indicates the remarkable functional specialization of the affected regions of the Y chromosome.

Base Sequence↗

PubMed2002

Reduced copy number of DAZ genes in subfertile and infertile men.

OBJECTIVE(S): To determine the copy number and identity of the DAZ genes on the Y chromosomes of infertile patients. DESIGN: Prospective study. SETTING: University medical center. PATIENT(S): One hundred and thirty-nine patients with male factor infertility. INTERVENTION(S): The separate genes were detected by polymerase chain reaction (PCR) digestion assays of sequence family variants in leukocyte DNA and by fluorescence in situ hybridization of interphase nuclei and chromatin fibers. MAIN OUTCOME MEASURE(S): Number of DAZ genes present. RESULT(S): One hundred twenty-nine patients had four genes, 6 patients had two genes, and 4 patients had none. Three patients had a deletion of the two proximal DAZ genes, and three were missing both distal genes. Semen analysis showed a less severe phenotype in patients with only two DAZ genes compared with patients missing all four genes. CONCLUSION(S): In six patients, two different partial deletions were found that were not detected by PCR with conventional markers. One patient with an AZFb deletion appeared to also have a partial AZFc deletion that was not detected by routine PCR. Phenotypic differences between patients with different deletions suggest a dose effect of the DAZ genes.

Amino Acid Substitution↗

PubMed2002

Use of the total motile sperm count to predict total fertilization failure in in vitro fertilization.

OBJECTIVE: To evaluate the capacity of baseline characteristics and total motile sperm count (TMC) to predict total fertilization failure (TFF) in patients undergoing IVF. DESIGN: Retrospective cohort study. SETTING: University hospital. PATIENT(S): Eight hundred ninety-two couples with a total of 1,569 consecutive IVF cycles. INTERVENTION(S): Prewash and postwash TMC during fertility workup and at the time of ovum pickup (OPU). MAIN OUTCOME MEASURE(S): Analysis of logistic regression and the receiver operating characteristic curve were used to determine which variables could be used to predict TFF. RESULT(S): The area under the curve (AUC) for prewash TMC during fertility workup was 0.72, similar to a combination of pre- and postwash TMC. At the time of OPU, both pre- and postwash TMC had an AUC of 0.73. A model based on selected baseline characteristics (male age, number of IVF cycles, indication for IVF, and prewash TMC during fertility workup) had an AUC of 0.75. A model at the time of OPU, including the number of oocytes, had an AUC of 0.80. CONCLUSION(S): The use of both models, one before start of the IVF cycle and one at the time of OPU, allows an accurate prediction of the chance of TFF and is useful in counseling patients on whether to opt for IVF or ICSI.

Adult↗

PubMed2002

Clinical relevance of partial AZFc deletions.

To determine the number of DAZ gene clusters in the Y-bearing spermatozoa of patients who underwent intracytoplasmic sperm injection (ICSI) and to compare the outcome with the number of clusters found in the spermatozoa of normospermic men. Prospective study. Academic hospital.Forty-seven patients with impaired spermatogenesis who were attending our clinic for ICSI and 56 semen donors. Peripheral blood was drawn to obtain somatic DNA for polymerase chain reaction (PCR) analysis and leukocytes for karyotyping and FISH analysis. Three-color FISH was performed on the spermatozoa remaining after ICSI and on the spermatozoa of semen donors to determine the presence of the X and Y chromosome as well as the number of DAZ gene clusters. Number of DAZ gene clusters in Y-bearing spermatozoa. Five patients had only one DAZ gene cluster, one patient had a complete AZFc deletion, and one patient had three clusters on average. One of the semen donors also showed three DAZ gene clusters in his Y-bearing spermatozoa. None of the semen donors had only one DAZ gene cluster. Besides complete AZFc deletions, partial deletions are also associated with impaired spermatogenesis. As a result, these partial deletions that are not recognized by routine PCR are reintroduced into the population by the ICSI technique.

Chromosomes, Human, Y↗

PubMedDate not supplied

Transmission of male infertility to future generations: lessons from the Y chromosome.

The introduction of ICSI and testicular sperm extraction (TESE) has allowed many infertile men to father children. The biggest concern about the wide use of these techniques is the health of the resulting offspring, in particular their fertility status. If the spermatogenic defect is genetic in origin, there is potential risk of transmitting this defect to future offspring. The most frequently documented genetic cause of male infertility is a Y chromosome deletion. The Y chromosome has acquired a large number of testis-specific genes during recent evolution, and deletions causing infertility take out a number of these genes. These deletions have been shown to be transmitted to 100% of male offspring. Also, absence of an aberration on the Y chromosome does not rule out a genetic cause of the infertility phenotype, as there are many other genes involved in spermatogenesis elsewhere in the genome, and current mapping techniques--especially on the Y chromosome--can miss many aberrations. More detailed studies of these spermatogenesis genes, which are now possible because of more precise sequence-based mapping, will lead to improved understanding of the genetic basis of male infertility and enable proper counselling of patients undergoing ICSI in the future.

Chromosomes, Human, Y↗