Steroid 5alpha-reductase 2 gene melting polymorphisms in male subjects with azoospermia or oligospermia

OBJECTIVE

This study was designed to test the hypothesis that mutations in the gene for type 2 steroid 5alpha-reductase (SRD5A2) may be the cause of a phenotype characterized primarily by oligospermia or azoospermia.

STUDY DESIGN

Deoxyribonucleic acid from control subjects and subjects with oligospermia (n = 12) and azoospermia (n = 6) were evaluated for mutations in SRD5A2. Methods used for mutation analysis included polymerase chain reaction, Southern blotting, and denaturing gradient gel electrophoresis.

RESULTS

Denaturing gradient gel electrophoresis of all 5 amplified exons resulted in similar migration patterns in samples from both control and study subjects. Genomic deoxyribonucleic acid subjected to denaturing gradient gel electrophoresis after restriction digest revealed melting polymorphisms. Direct sequencing of the gene in a single patient with a unique melting polymorphism yielded a normal sequence.

CONCLUSIONS

Melting polymorphisms for SRD5A2 were detected in a group of patients with oligospermia or azoospermia. Sequence analysis did not demonstrate functional mutations in the coding sequence of this gene.

Molecular biology and reproduction

Modern molecular biology has provided unique insights into the fundamental understanding of reproductive disorders and the detection of microorganisms. The remarkable advances in DNA diagnostics have been expedited by the development of polymerase chain reaction (PCR) and the ability to isolate DNA and RNA from many different sources such as blood, saliva, hair roots, microscopic slides, paraffin-embedded tissue sections, clinical swabs, and even cancellous bone. These technical advances have been bolstered by the development of an increasing number of effective screening techniques to scan genomic DNA for unknown point mutations. The continued development of technology will ultimately result in automated DNA (desoxyribonucleic acid) diagnosis for the practicing clinician. The continuing expansion of information concerning the human genome will place an increasing emphasis on bioinformatics and the use of computer software for analyzing DNA sequences. With the automation of DNA diagnosis and the use of small samples (500 nanograms), the direct examination of the DNA of a patient, fetus, or microorganism will emerge as a definitive means of establishing the presence of the specific genetic change that causes disease. A knowledge of the precise pathology at the molecular level has and will provide important insights into the biochemical basis for many human diseases. A firm knowledge of the DNA alterations in disease and expression patterns of specific genes will provide for more directed therapeutic strategies. The refinement of vector technology and nuclear transplantion techniques will provide the opportunity for directed gene therapy to the early human embryo. This presentation is designed to acquaint the reader with current techniques of testing at the DNA level, prototype mutations in the reproductive sciences, new concepts in the molecular mechanisms of disease that affect reproduction, and therapeutic opportunities for the future. It is hoped that future refinement of these techniques combined with the ability to maintain genetic modification of these cells with recombinant vector technology will provide a definitive therapy for many single gene disorders, such as sickle cell anemia and thalassaemia. It is truly the challenge of the next century to decipher how these legions of newly discovered genes work, and to create a molecular language that can extend across all organisms.

The Y-chromosome and reproductive disorders

Over the past decade the tools of modern molecular biology have provided unique insights into our fundamental understanding of developmental systems. These insights have been gleaned from the study of a wide variety of model organisms including yeast (Saccharomyces cerevisiae), fly (Drosophila), worm (Caenorhabditis elegans), and mouse. In man, the first analysis of developmental systems started with sexual differentiation and focused on the role of Y-linked genes. The presence of living developmental mutants in man affecting sexual development and the early technology of deletion mapping facilitated the isolation and identification of small segments of putative DNA suspected to contain sex-determining genes. The isolation of genes such as SRY (Sex Related gene on Y) has provided the first insights into the molecular biology of human sexual differentiation. The focus on the Y chromosome has brought further insights into chromosomal pairing, statural determinants in man, oncogenesis, spermatogenesis, haploid genomes, and the lineage of man himself. This paper provides the circumstantial and direct evidence to illustrate the importance of the Y chromosome in reproductive disorders, and in the analysis of haploid genomes.

The role of p53 tumor suppressor gene and bcl-2 protooncogene in rat corpus luteum death

OBJECTIVE

The purpose of this study was to find out whether the mammalian corpus luteum undergoes genetically programmed cell death as evidenced by the positive or negative expression of specific biochemical markers of apoptosis (p53 and bcl-2).

STUDY DESIGN

Twenty-six immature 28-day-old female Sprague-Dawley rats were given 10 IU of pregnant mare's serum gonadotropin to induce ovulation and corpus luteum formation. Corpora lutea were collected on postovulatory days 8, 10, 12, and 14 and snap-frozen immediately. Determinations of apoptotic fragmentation of deoxyribonucleic acid were performed with use of samples radiolabeled at 3'-ends with deoxynucleotide alpha-phosphorus 32-deoxycytidine triphosphate (3000 Ci/mmol). Transcription of p53 and bcl-2 was determined by Northern blot analysis of total ribonucleic acid. Protein expression of p53 and bcl-2 was determined by Western blot analysis with a monoclonal rat antibody for p53 and a polyclonal rabbit antibody for bcl-2.

RESULTS

The nuclear fragmentation assay revealed formation of oligonucleosomes resulting in typical laddering of the deoxyribonucleic acid (corpus luteum) consistent with programmed cell death. Northern blot analysis of total ribonucleic acid prepared from immature (28-day-old) rat corpus luteum revealed the presence of a single p53 messenger ribonucleic acid transcript (2.1 kb) in all ages of corpus luteum studied from day 8 to day 14. Western blot analysis for p53 revealed a gradual reduction in p53 protein in corpus luteum from day 8 to day 12 until it became undetectable on day 14. Western blotting revealed expression of specific protein for bcl-2.

CONCLUSIONS

It appears that programmed cell death, as evidenced by formation of oligonucleosomes, occurs during mammalian luteal regression. The patterns of p53 ribonucleic acid expression in the corpus luteum suggest that the protein products of p53 and bcl-2 do not act in a diametric manner to regulate programmed cell death in the corpus luteum. The current results suggest that the mechanisms leading to programmed cell death in the mammalian corpus luteum may differ considerably from those in other organ systems.

The ethics of somatic and germline gene therapy

Somatic gene therapy research in humans is still searching for appropriate vector systems and remains experimental. Germline therapy is a major technical challenge and can be considered only for the future.

Oncogenic role of the Y chromosome

The mechanism to explain the oncogenic role of genomic YDNA in dysgenetic individuals remains uncertain. At this time, it is a statistically significant association, but without a biological explanation.

Human chorionic gonadotrophin-beta gene sequences in women with disorders of HCG production

Women with recurrent abortion, primary unexplained infertility, and gestational trophoblastic neoplasia (GTN) manifest disordered human chorionic gonadotrophin (HCG) secretion. Mutations in the HCG beta/luteinizing hormone (LH) beta gene complex could cause aberrant HCG production in these disorders. The purpose of this study was to determine whether HCG beta gene deletions occur in women with recurrent abortion or primary unexplained infertility, and whether HCG beta gene duplications are present in women with GTN. DNA was extracted from 10 patients with unexplained recurrent abortion, 10 patients with unexplained primary infertility, 12 patients with GTN, three partners of women with GTN, and 30 controls. Southern blots were constructed and hybridized with DNA probes for HCG beta-5 and the LH beta gene. No gene deletions were identified in patients with recurrent abortion or primary unexplained infertility. Likewise, no gene duplications were identified in women with GTN. A previously described Mbol restriction fragment length polymorphism (RFLP) was identified in both patients and controls. A new Pstl RFLP was also characterized, but was present in patients and controls. Deletion/duplication mutations in the HCG beta/LH beta gene complex do not appear to be common causes of aberrant HCG production in humans with these disorders.

Paternal somatic and germ-line mosaicism for a sex-determining region on Y (SRY) missense mutation leading to recurrent 46,XY sex reversal

OBJECTIVE

To determine the etiology for recurrent 46,XY sex reversal in a family with two Swyer siblings.

DESIGN

Deoxyribonucleic acid (DNA) from peripheral lymphocytes and sperm were analyzed for duplication of the dosage sensitive sex locus (DSS) and for mutations in sex-determining region on Y (SRY).

SETTING

An academic teaching hospital.

PATIENTS

A family consisting of mother, father, and five phenotypic daughters, of which two were 46,XY sex-reversed females.

INTERVENTION

Deoxyribonucleic acid (DNA) extraction, polymerase chain reaction (PCR), Southern blotting, dosage densitometry, single-strand conformation polymorphism (SSCP), and sequencing.

MAIN OUTCOME MEASURE

Comparison of control and subject DNA.

RESULTS

Deoxyribonucleic acid (DNA) analysis of SRY in genomic DNA from the 46,XY sex-reversed siblings revealed identical missense mutations (T-->G) in both sisters. Analysis of the SRY gene in paternal lymphocyte and sperm DNA revealed mosaicism for wild and mutant (T-->G) SRY sequences. SRY analysis of sperm DNA also demonstrated the same mosaicism for the T-->G missense mutation.

CONCLUSION

A postembryonic SRY mutation gave rise to paternal mosaicism for two distinct cell populations (SRY+/SRY-). The presence of a wild type SRY in the somatic cell line may account for a normal pattern of male sexual differentiation, whereas the presence of a mutated SRY in the germ line resulted in two 46,XY sex-reversed offspring. These results confirm a proposed mechanism for the condition of recurrent 46,XY sex-reversed females.

Massive ovarian enlargement in primary hypothyroidism

OBJECTIVE

To report a case of ovarian cyst formation and myxedematous infiltration of the ovary in a subject with primary hypothyroidism.

DESIGN

Retrospective case report.

SETTING

University hospital.

PATIENT(S)

A 16-year-old female adolescent with pelvic pain, galactorrhea, irregular menses, and ovarian cysts on pelvic examination.

INTERVENTION(S)

Laparotomy with bilateral ovarian wedge resection and thyroid replacement therapy.

MAIN OUTCOME MEASURE(S)

Ovarian histopathology, thyroid function tests, and menstrual history.

RESULT(S)

Resolution of patient's pain, galactorrhea, and resumption of normal menses.

CONCLUSION(S)

Ovarian cyst formation may accompany primary hypothyroidism in the child with accelerated or delayed sexual maturation. To date, the underlying pathophysiology of the morphological changes in the ovary remain enigmatic. This case report provides the first insight into the actual histologic changes that occur in ovaries of subjects with primary hypothyroidism without secondary ovarian pathology such as torsion. There is clear evidence of myxedematous infiltration into the ovarian stroma without luteinization of the theca interna. These microscopic findings suggest that local changes occurring independent of gonadotropin stimulation may contribute significantly to altered morphology of the ovaries in primary hypothyroidism.