In cases of severe teratozoospermia, the current morphological criteria used to assess chromosomal status is insufficient for the selection of spermatozoa for intracytoplasmic sperm injection (ICSI). Case histories are reported of four patients presenting 100% teratozoospermia, and the integrity of their individual chromosomal statuses is determined using a three-colour fluorescence in-situ hybridization (FISH) technique. Patient 1 presented shortened flagella syndrome, patient 2 globozoospermia, patient 3 spermatozoa with irregular acrosomes, and patient 4 macrocephalic spermatozoa with associated multiple flagella. Three-colour FISH analysis using chromosome X, Y and 1-specific probes showed that approximately 95% of the spermatozoa analysed from patients 1, 2 and 3 presented X,1 and Y,1 signals, X,Y ratios and aneuploidy/diploidy rates comparable with those observed in normal controls. In contrast, patient 4 showed a highly elevated Y to X sex ratio and a highly elevated aneuploidy/diploidy rate. Three-colour FISH analysis thus demonstrates an increased incidence of chromosomal abnormalities in association with macrocephalic spermatozoa. Moreover, the analysis shows that in patients affected with either globozoospermia, shortened flagella syndrome or a condition of abnormal acrosomal spermatozoa, no association exists between chromosomal status and phenotype. Since these patients display normal haploid, sex chromosome and aneuploidy status, ICSI can be conceivably offered as a treatment for their infertility.
The three murine retinoic acid receptor (RAR) genes each contain two distinct promoters which give rise to protein isoforms differing in their N-terminal regions. This study used in situ hybridization to describe the expression patterns of RARalpha1, RARalpha2, RARbeta1/3, RARbeta2/4, RARgamma1 and RARgamma2 isoform transcripts during mouse embryogenesis. RARalpha1 transcripts are widely distributed, with the exception of the central nervous system. Highest expression is found in developing muscle, pituitary gland and various epithelia. On the other hand, RARalpha2 is essentially expressed along the spinal cord up to the hindbrain 7th rhombomere and in the 4th rhombomere, pons and developing basal ganglia (corpus striatum and pallidum). RARbeta2/4 transcripts account for most of the previously described RARbeta expression features being expressed specifically, or more prominently than RARbeta1/3, in foregut endoderm and its derivatives, olfactory and periocular mesenchyme, urogenital region, proximal limb bud mesenchyme and later within interdigital regions. RARbeta1/3 is more prominently expressed in the developing heart outflow tract mesenchyme, intervertebral disks, midgut loop mesenchyme and umbilical vessel walls. RARbeta1/3 and RARbeta2/4 are coexpressed in the developing corpus striatum. They exhibit, however, distinct dorsoventral distributions along the spinal cord and caudal hindbrain. RARgamma2 is the RARgamma isoform expressed at high levels in the caudal neural groove at embryonic day 8.5. At later stages, both RARgamma isoforms are essentially coexpressed, although the progressive restriction of RARgamma1 transcripts to craniofacial or limb precartilaginous condensations appears to precede that of RARgamma2.
Studies into the mechanisms underlying spermatogenesis, the process by which spermatogonia undergo meiosis to become spermatozoa, have identified a number of genetic determinants of male infertility. Indeed, a more comprehensive knowledge of the genetic regulation of spermatogenesis has alleviated the dependence on the use of idiopathic infertility as a classification for sterile men for whom a cause for their infertility is unknown, as genetic factors become more accountable for this phenotype. This review focuses on selected areas implicated in male infertility including: (i) autosomal and sex chromosomal abnormalities; (ii) genetic disorders associated with impaired gonadotrophin secretion or action; (iii) microdeletions within regions of the Y-chromosome containing candidate gene families for spermatogenesis; (iv) the genetic nexus between cystic fibrosis and congenital bilateral absence of the vas deferens; and (v) insights into human infertility as gleaned from animal studies into mechanisms involving the Bcl-2 family of apoptosis regulators and the interaction between the c-kit encoded tyrosine kinase receptor and its ligand, stem cell factor. As significant advances continue to further knowledge of the genetic basis of male infertility, such as those leading to an understanding of the aforementioned areas, greater progress can be made to rectify or at least ameliorate social stigmas associated with sterility.
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