A. Edelmann

Bio: A. Edelmann is an academic researcher from Heidelberg University. The author has contributed to research in topics: Azoospermia factor & Gene. The author has an hindex of 2, co-authored 2 publications receiving 1324 citations. Previous affiliations of A. Edelmann include University of Marburg.

Human Y Chromosome Azoospermia Factors (AZF) Mapped to Different Subregions in Yq11

Abstract: In a large collaborative screening project, 370 men with idiopathic azoospermia or severe oligozoospermia wereanalysed for deletions of 76 DNA loci in Yq11. In 12 individuals, we observed de novo microdeletions involvingseveral DNA loci, while an additional patient had an inherited deletion. They were mapped to three differentsubregions in Yq11. One subregion coincides to the AZF region defined recently in distal Yq11. The second andthird subregion were mapped proximal to it, in proximal and middle Yq11, respectively. The different deletionsobserved were not overlapping but the extension of the deleted Y DNA in each subregion was similar in eachpatient analysed. In testis tissue sections, disruption of spermatogenesis was shown to be at the same phasewhen the microdeletion occurred in the same Yq11 subregion but at a different phase when the microdeletionoccurred in a different Yq11 subregion. Therefore, we propose the presence of not one but three spermatogenesisloci in Yq11 and that each locus is active during a different phase of male germ cell development. As the mostsevere phenotype after deletion of each locus is azoospermia, we designated them as: AZFa, AZFb and AZFc.Their probable phase of function in human spermatogenesis and candidate genes involved will be discussed. INTRODUCTIONGenes for male germ cell development are present on the Ychromosome in different species groups (1–3). In men, theposition of a spermatogenesis locus was mapped in theeuchromatic part of the long Y arm (Yq11). It was called‘azoospermia factor’ (AZF), as the first six men observed withterminal deletions in Yq were azoospermic (4). Mature spermcells were not detectable in their seminal fluid. In all cases, the Ydeletions included the large heterochromatin block of the long Yarm (Yq12) and an undefined amount of the adjacent euchromatin(Yq11). Subsequently, the presence of AZF in Yq11 wasconfirmed by numerous studies at both cytogenetic (5) andmolecular level (6–8). However, the genetic complexity of AZFcould not be revealed by these analyses.This first became possible by the detection of sterile patientswith small interstitial deletions (i.e. microdeletions) in Yq11. Ina study with 13 sterile men suffering from idiopathic azoospermiatwo different microdeletions in Yq11 were observed (9). Theywere mapped to two non overlapping positions in Yq11 interval6 (10). However, further studies of Yq11 microdeletionsassociated to the phenotype of male sterility, only confirmed theposition of an AZF locus in distal Yq11 (11,12). The mostextensive study was performed by Reijo et al. (13) on 89 sterile

DAZ (Deleted in AZoospermia) genes encode proteins located in human late spermatids and in sperm tails.

Abstract: We analysed the location of proteins encoded by the DAZ (Deleted in AZoospermia) genes in human testis tissue and in mature spermatozoa. The DAZ genes are known to be expressed exclusively in the human male germ line, and are candidate genes for the expression of the azoospermia factor AZFc mapped recently to distal Yq11. They encode testis-specific RNA binding proteins, the function of which is not yet known. Immunostaining experiments with antibodies prepared for the specific peptide domain encoded by the DAZ2 transcript (formerly SPGY1) revealed the presence of DAZ proteins in the innermost layer of the male germ cell epithelium and in the tails of spermatozoa. This suggests a function for DAZ proteins in the RNA metabolism of late spermatids, presumably in the storage or transport of testis-specific mRNA, the translation of which is repressed until the formation of mature spermatozoa. Deletion of DAZ genes is supposed not to interfere with human sperm maturation but to result in a gradual reduction of mature spermatozoa.

Multiplex PCR: critical parameters and step-by-step protocol.

Abstract: By simultaneously amplifying more than one locus in the same reaction, multiplex PCR is becoming a rapid and convenient screening assay in both the clinical and the research laboratory. While numerous papers and manuals discuss in detail conditions influencing the quality of PCR in general, relatively little has been published about the important experimental factors and the common difficulties frequently encountered with multiplex PCR. We have examined various conditions of the multiplex PCR, using a large number of primer pairs. Especially important for a successful multiplex PCR assay are the relative concentrations of the primers at the various loci, the concentration of the PCR buffer, the cycling temperatures and the balance between the magnesium chloride and deoxynucleotide concentrations. Based on our experience, we propose a protocol for developing a multiplex PCR assay and suggest ways to overcome commonly encountered problems.

Functional coherence of the human Y chromosome.

Abstract: A systematic search of the nonrecombining region of the human Y chromosome (NRY) identified 12 novel genes or families, 10 with full-length complementary DNA sequences. All 12 genes, and six of eight NRY genes or families previously isolated by less systematic means, fell into two classes. Genes in the first group were expressed in many organs; these housekeeping genes have X homologs that escape X inactivation. The second group, consisting of Y-chromosomal gene families expressed specifically in testes, may account for infertility among men with Y deletions. The coherence of the NRY's gene content contrasts with the apparently haphazard content of most eukaryotic chromosomes.

Oxidative stress, DNA damage and the Y chromosome.

Abstract: Recent advances in understanding of male infertility have implicated two major causative factors, oxidative stress and Y chromosome deletions. A major cause of oxidative stress appears to be the high rate of reactive oxygen species generation associated with the retention of excess residual cytoplasm in the sperm midpiece. Other possible causes include the redox cycling of xenobiotics, and antioxidant depletion or apoptosis. Oxidative stress induces peroxidative damage in the sperm plasma membrane and DNA damage in both the mitochondrial and nuclear genomes. Nuclear DNA damage in the germ line of the father may be associated with pathology in the offspring, including childhood cancer and infertility. Gene deletions on the non-recombining region of the Y chromosome account for the infertility observed in about 15% of patients with azoospermia and 5-10% of subjects with severe oligozoospermia. The Y chromosome is particularly susceptible to gene deletions because of the inability of the haploid genome to deploy recombination repair in retrieving lost genetic information. Aberrant recombination, defective chromatin packaging, abortive apoptosis and oxidative stress may all be involved in the aetiology of DNA damage in the germ line. The factors responsible for Y chromosome deletions in spermatozoa remain unresolved but may be one facet of a central reproductive problem: controlling the amount of oxidative stress experienced by germ cells during their differentiation and maturation in the male reproductive tract.