The deleted in azoospermia like (DAZL) gene has been identified in many vertebrate species. DAZL shows high homology with deleted in azoospermia (DAZ) genes that identified only in humans, great apes and Old World monkeys, and boule homolog (BOLL) that identified in many vertebrate species. These genes encode RNA binding proteins (RBP), which regulate the post-transcriptional functions of several genes. In humans, DAZ copies are linked to Y chromosome, while DAZL and BOLL are linked to chromosomes 3 and 2, respectively. DAZ copies has been reported to express in prenatal and postnatal germ cells, particularly in the premeiotic spermatogonia. BOLL has been reported to express during the meiotic G2/M transition in germ cells. DAZL has been reported to express in all stages of germ cells. Compared to humans and mice, the detailed functionalities of DAZL is not clear in many vertebrate species. In our studies, we use chickens as an animal model to examine the expression profiling of DAZL gene in germ cells right from the early embryonic development to the adult. Also, we are studying the effects of small interfering RNA (siRNA) mediated knockdown of DAZL and Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)/CRISPR associated protein 9 (CRISPR/Cas9) mediated knockout of DAZL in the chicken primordial germ cells (PGCs). In the chicken, DAZL is linked to chromosome 2 (2p1.3-p1.2), and encodes a 289 amino acids protein. By in situ hybridization, we detected a strong expression of DAZL in the germ plasm of chicken oocytes. Later, the expression of DAZL was strongly detected in all stages of intrauterine development and post-ovipositional development especially in the PGC specifying cells. Moreover, the expression of DAZL was strong and constant in the male and female germ cells until adult stage. The siRNA mediated knockdown of DAZL significantly reduced the PGCs proliferation and increased the apoptosis in vitro. We examined the knockout efficiency of DAZL using CRISPR/Cas9 technique in chicken DF1 fibroblast cell line, prior to test in the PGCs. The results of T7 endonuclease I (T7E1) assay and subsequent sequencing indicates clear mutations on the DAZL gene in DF1 cells, and the method could be applicable to cause mutations on the DAZL gene in PGCs. In conclusion, chicken DAZL express in all stages of germ cells as a germ line marker, and alteration in the gene expression causes germ cells impairment.

The Y chromosome is a type of sex chromosome existing primarily in male mammalian species. The Y chromosome passes through the male gamete and determines male sex in humans, non-human primates, and other mammals. The mammalian Y chromosome varies from the X chromosome and the rest of the chromosomes primarily by size and its male sex-determining/spermatogenesis function. In the Y chromosome, male sex-determining function is exclusively located on the short arm, while the spermatogenesis function is distributed widely on the short and long arm. Deletions or mutations particularly in the male-specific region of Y chromosome (MSY) may cause male infertility. During the last few decades, researchers put forth an enormous effort to discover Y chromosome specific genes, and their encoded RNAs and proteins in humans, primates, and rodents. As a result, most of the genes and encoded proteins responsible for male-sex determination, testis development, and spermatogenesis have been discovered in humans, however not well established in non-human primates and rodents. Also, there might be a percent of proteins missing in human Y chromosome. The aim of this study is to annotate the proteins that encoded on the Y chromosome of humans, chimpanzee, and mouse using extensive bioinformatics tools. The human (annotation release 107), chimpanzee (annotation release 103), and mouse (annotation release 105) proteins were first retrieved from the National Center for Biotechnology Information (NCBI) eukaryotic genome annotation resource database. Then, the annotated human proteins (66 proteins) were compared with the core databases of human proteome project such as neXtProt, PeptideAtlas, and the Human Protein Atlas. The X-homologous of human Y chromosome-encoded proteins were searched using the NCBI Protein BLAST program. The cellular pathways and protein-protein interactions involving human Y chromosome-encoded proteins were searched using the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway mapping database, the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database, and the Pathway Studio software. Finally, the human Y chromosome-encoded protein homologs/orthologs in chimpanzee and mouse were analyzed using the NCBI bl2seq program. This analysis resulted a significant number of homologous/orthologous proteins between human, chimpanzee and mouse. Our findings provide the scientific community with updated information on the Y chromosome-encoded proteins in humans, chimpanzee, and mouse.