O objetivo deste trabalho foi o de avaliar o efeito da suplementação da dieta de Tilápias (Oreochromis niloticus) utilizando sal comercial composto dos microminerais cobre, manganês e zinco, sobre a histologia e o desenvolvimento das gônadas dos machos. Foram utilizados 1200 machos masculinizados de tilápia, com média de peso de 120g, suplementadas com níveis crescentes (0,00; 0,35; 0,70; 1,05; 1,40 e 1,75 mg/kg) de um produto comercial composto por Cu 13,40 g/kg; Mn 26,70 g/kg e Zn 66,70 g/kg. O experimento foi conduzido em um sistema de recirculação de água, composto por 24 tanques divididos ao meio totalizando 48 unidades experimentais. O delineamento experimental foi inteiramente casualizado, com medidas repetidas no tempo. As biometrias e coletas foram realizadas em 16 e 32 semanas de experimento, para avaliar o desenvolvimento dos peixes. As gônadas coletadas foram preparadas e cortadas para confecção de lamina histológica, após coradas com hematoxilina e eosina, e posteriormente fotografadas, utilizando microscópio com câmera acoplada. A contagem das fotos foi realizada manualmente, e avaliou-se o número de células por mm3, para espermatogônias, espermatócitos, espermátides e espermatozoides. As correlações entre número de espermatozoides, espermatócitos, espermátides e tratamentos foi de -0,30, -0,20 e -0,30, respectivamente, demonstrando que o efeito da suplementação crescente com o sal, é prejudicial para o desenvolvimento das células reprodutivas masculinas. Foi observado que os tratamentos com adição igual ou superior a 0,70 mg/kg do sal comercial causaram danos as gônadas para os parâmetros da gametogênese de número de espermatócitos, espermátides e espermatozoides. Sendo assim, a utilização de sais que contenham combinação de Cu 13,40 g/kg; Mn 26,70 g/kg e Zn 66,70 g/kg reprodutores machos de tilápia, não é recomendada em função dos danos causados nas etapas da gametogênese, reduzindo a produção de espermatozoides. / The objective of this study was to evaluate the effect of supplementing the diet of tilapia (Oreochromis niloticus) using commercial salt compound of micro minerals copper, manganese and zinc, on the histology and gonadal development of males. A total of 1200 masculinized male tilapia were used, with 120 g average weight, supplemented with increasing levels (0.00, 0.35, 0.70, 1.05, 1.40 and 1.75 mg / kg) of a product commercial composed of Cu 13,40 g/kg; Mn 26,70 g/kg e Zn 66,70 g/kg. The trial was conducted in a water recirculation system, consisting of 24 tanks divided in half, totaling 48 experimental units. The experimental design was completely randomized with repeated measures over time. The biometry and samples were taken at 16 and 32 weeks of experiment, to evaluate the fish development. The collected gonads were prepared and sliced for making histological slide, after stained with hematoxylin and eosin, and then photographed using a microscope with attached camera. The count of the photos was performed manually, and was rated the number of cells per mm3 to spermatogonia, spermatocytes, spermatids and sperm cell. The correlations between the number of spermatozoa, spermatocytes, spermatids and treatments was of -0.30, -0.20 and -0.30, respectively, demonstrating that the effect of increasing supplementation of the salt is detrimental to the development of male reproductive cells. It was observed that the addition equal or superior to 0.70 mg / kg of commercial salt caused damage in the gonads for gametogenesis parameters number of spermatocytes, spermatids and sperma cell. Thus, the use of combination of salts containing 13.40 g Cu / kg; Mn 26.70 g / kg Zn and 66.70 g / kg breeding male tilapia is not recommended due to the damage caused in the stages of gametogenesis, reducing the sperm production.

O objetivo deste trabalho foi o de avaliar o efeito da suplementação da dieta de Tilápias (Oreochromis niloticus) utilizando sal comercial composto dos microminerais cobre, manganês e zinco, sobre a histologia e o desenvolvimento das gônadas dos machos. Foram utilizados 1200 machos masculinizados de tilápia, com média de peso de 120g, suplementadas com níveis crescentes (0,00; 0,35; 0,70; 1,05; 1,40 e 1,75 mg/kg) de um produto comercial composto por Cu 13,40 g/kg; Mn 26,70 g/kg e Zn 66,70 g/kg. O experimento foi conduzido em um sistema de recirculação de água, composto por 24 tanques divididos ao meio totalizando 48 unidades experimentais. O delineamento experimental foi inteiramente casualizado, com medidas repetidas no tempo. As biometrias e coletas foram realizadas em 16 e 32 semanas de experimento, para avaliar o desenvolvimento dos peixes. As gônadas coletadas foram preparadas e cortadas para confecção de lamina histológica, após coradas com hematoxilina e eosina, e posteriormente fotografadas, utilizando microscópio com câmera acoplada. A contagem das fotos foi realizada manualmente, e avaliou-se o número de células por mm3, para espermatogônias, espermatócitos, espermátides e espermatozoides. As correlações entre número de espermatozoides, espermatócitos, espermátides e tratamentos foi de -0,30, -0,20 e -0,30, respectivamente, demonstrando que o efeito da suplementação crescente com o sal, é prejudicial para o desenvolvimento das células reprodutivas masculinas. Foi observado que os tratamentos com adição igual ou superior a 0,70 mg/kg do sal comercial causaram danos as gônadas para os parâmetros da gametogênese de número de espermatócitos, espermátides e espermatozoides. Sendo assim, a utilização de sais que contenham combinação de Cu 13,40 g/kg; Mn 26,70 g/kg e Zn 66,70 g/kg reprodutores machos de tilápia, não é recomendada em função dos danos causados nas etapas da gametogênese, reduzindo a produção de espermatozoides. / The objective of this study was to evaluate the effect of supplementing the diet of tilapia (Oreochromis niloticus) using commercial salt compound of micro minerals copper, manganese and zinc, on the histology and gonadal development of males. A total of 1200 masculinized male tilapia were used, with 120 g average weight, supplemented with increasing levels (0.00, 0.35, 0.70, 1.05, 1.40 and 1.75 mg / kg) of a product commercial composed of Cu 13,40 g/kg; Mn 26,70 g/kg e Zn 66,70 g/kg. The trial was conducted in a water recirculation system, consisting of 24 tanks divided in half, totaling 48 experimental units. The experimental design was completely randomized with repeated measures over time. The biometry and samples were taken at 16 and 32 weeks of experiment, to evaluate the fish development. The collected gonads were prepared and sliced for making histological slide, after stained with hematoxylin and eosin, and then photographed using a microscope with attached camera. The count of the photos was performed manually, and was rated the number of cells per mm3 to spermatogonia, spermatocytes, spermatids and sperm cell. The correlations between the number of spermatozoa, spermatocytes, spermatids and treatments was of -0.30, -0.20 and -0.30, respectively, demonstrating that the effect of increasing supplementation of the salt is detrimental to the development of male reproductive cells. It was observed that the addition equal or superior to 0.70 mg / kg of commercial salt caused damage in the gonads for gametogenesis parameters number of spermatocytes, spermatids and sperma cell. Thus, the use of combination of salts containing 13.40 g Cu / kg; Mn 26.70 g / kg Zn and 66.70 g / kg breeding male tilapia is not recommended due to the damage caused in the stages of gametogenesis, reducing the sperm production.

O objetivo deste trabalho foi o de avaliar o efeito da suplementação da dieta de Tilápias (Oreochromis niloticus) utilizando sal comercial composto dos microminerais cobre, manganês e zinco, sobre a histologia e o desenvolvimento das gônadas dos machos. Foram utilizados 1200 machos masculinizados de tilápia, com média de peso de 120g, suplementadas com níveis crescentes (0,00; 0,35; 0,70; 1,05; 1,40 e 1,75 mg/kg) de um produto comercial composto por Cu 13,40 g/kg; Mn 26,70 g/kg e Zn 66,70 g/kg. O experimento foi conduzido em um sistema de recirculação de água, composto por 24 tanques divididos ao meio totalizando 48 unidades experimentais. O delineamento experimental foi inteiramente casualizado, com medidas repetidas no tempo. As biometrias e coletas foram realizadas em 16 e 32 semanas de experimento, para avaliar o desenvolvimento dos peixes. As gônadas coletadas foram preparadas e cortadas para confecção de lamina histológica, após coradas com hematoxilina e eosina, e posteriormente fotografadas, utilizando microscópio com câmera acoplada. A contagem das fotos foi realizada manualmente, e avaliou-se o número de células por mm3, para espermatogônias, espermatócitos, espermátides e espermatozoides. As correlações entre número de espermatozoides, espermatócitos, espermátides e tratamentos foi de -0,30, -0,20 e -0,30, respectivamente, demonstrando que o efeito da suplementação crescente com o sal, é prejudicial para o desenvolvimento das células reprodutivas masculinas. Foi observado que os tratamentos com adição igual ou superior a 0,70 mg/kg do sal comercial causaram danos as gônadas para os parâmetros da gametogênese de número de espermatócitos, espermátides e espermatozoides. Sendo assim, a utilização de sais que contenham combinação de Cu 13,40 g/kg; Mn 26,70 g/kg e Zn 66,70 g/kg reprodutores machos de tilápia, não é recomendada em função dos danos causados nas etapas da gametogênese, reduzindo a produção de espermatozoides. / The objective of this study was to evaluate the effect of supplementing the diet of tilapia (Oreochromis niloticus) using commercial salt compound of micro minerals copper, manganese and zinc, on the histology and gonadal development of males. A total of 1200 masculinized male tilapia were used, with 120 g average weight, supplemented with increasing levels (0.00, 0.35, 0.70, 1.05, 1.40 and 1.75 mg / kg) of a product commercial composed of Cu 13,40 g/kg; Mn 26,70 g/kg e Zn 66,70 g/kg. The trial was conducted in a water recirculation system, consisting of 24 tanks divided in half, totaling 48 experimental units. The experimental design was completely randomized with repeated measures over time. The biometry and samples were taken at 16 and 32 weeks of experiment, to evaluate the fish development. The collected gonads were prepared and sliced for making histological slide, after stained with hematoxylin and eosin, and then photographed using a microscope with attached camera. The count of the photos was performed manually, and was rated the number of cells per mm3 to spermatogonia, spermatocytes, spermatids and sperm cell. The correlations between the number of spermatozoa, spermatocytes, spermatids and treatments was of -0.30, -0.20 and -0.30, respectively, demonstrating that the effect of increasing supplementation of the salt is detrimental to the development of male reproductive cells. It was observed that the addition equal or superior to 0.70 mg / kg of commercial salt caused damage in the gonads for gametogenesis parameters number of spermatocytes, spermatids and sperma cell. Thus, the use of combination of salts containing 13.40 g Cu / kg; Mn 26.70 g / kg Zn and 66.70 g / kg breeding male tilapia is not recommended due to the damage caused in the stages of gametogenesis, reducing the sperm production.

The cohesin complex is essential for mitosis and meiosis. The specific meiotic roles of individual cohesin proteins are incompletely understood. We report in vivo functions of the only meiosis-specific STAG component of cohesin, STAG3. Newly generated STAG3-deficient mice of both sexes are sterile with meiotic arrest. In these mice, meiotic chromosome architecture is severely disrupted as no bona fide axial elements (AE) form and homologous chromosomes do not synapse. Axial element protein SYCP3 forms dot-like structures, many partially overlapping with centromeres. Asynapsis marker HORMAD1 is diffusely distributed throughout the chromatin, and SYCP1, which normally marks synapsed axes, is largely absent. Centromeric and telomeric sister chromatid cohesion are impaired. Centromere and telomere clustering occurs in the absence of STAG3, and telomere structure is not severely affected. Other cohesin proteins are present, localize throughout the STAG3-devoid chromatin, and form complexes with cohesin SMC1β. No other deficiency in a single meiosis-specific cohesin causes a phenotype as drastic as STAG3 deficiency. STAG3 emerges as the key STAG cohesin involved in major functions of meiotic cohesin.

The cohesin complex is essential for mitosis and meiosis. The specific meiotic roles of individual cohesin proteins are incompletely understood. We report in vivo functions of the only meiosis-specific STAG component of cohesin, STAG3. Newly generated STAG3-deficient mice of both sexes are sterile with meiotic arrest. In these mice, meiotic chromosome architecture is severely disrupted as no bona fide axial elements (AE) form and homologous chromosomes do not synapse. Axial element protein SYCP3 forms dot-like structures, many partially overlapping with centromeres. Asynapsis marker HORMAD1 is diffusely distributed throughout the chromatin, and SYCP1, which normally marks synapsed axes, is largely absent. Centromeric and telomeric sister chromatid cohesion are impaired. Centromere and telomere clustering occurs in the absence of STAG3, and telomere structure is not severely affected. Other cohesin proteins are present, localize throughout the STAG3-devoid chromatin, and form complexes with cohesin SMC1β. No other deficiency in a single meiosis-specific cohesin causes a phenotype as drastic as STAG3 deficiency. STAG3 emerges as the key STAG cohesin involved in major functions of meiotic cohesin.

Over the course of more than two decades, numerous studies have meticulously explored the fundamental roles of the cohesin complex, unraveling its intricate functions in sister chromatid cohesion, DNA recombination and repair, gene expression regulation, telomere protection, and regulatory mechanisms in cell division processes. However, the detailed and multifaceted roles of individual subunits within the cohesin complex during meiosis remain poorly understood. During my PhD, I focused my attention on two principal subunits that complete the tripartite ring: the meiotic isoform of SMC1, namely SMC1β, and a kleisin subfamily protein, RAD21. While RAD21 is the sole kleisin during mitosis, it is accompanied by two other kleisin subfamily proteins, REC8 and RAD21L, during meiosis. From past research, it is known that SMC1β is crucial for telomere protection in both spermatocytes and oocytes. Interestingly, while several major phenotypes of SMC1β-deficient spermatocytes were rescued by SMC1α, telomere abnormalities were not. The expression of telomerase and shelterin components appeared usual in SMC1β-deficient spermatocytes. This study highlights SMC1β's role in safeguarding telomeres at chromosome ends from damage and abnormalities by regulating the expression of a long non-coding RNA transcribed from the subtelomeres of different chromosomes, known as TERRA (Telomeric repeat–containing RNA). TERRA comprises repetitive sequence motifs transcribed from the telomeric DNA strand that is complementary to the DNA sequence of the telomere itself. SMC1β suppresses the expression of TERRA strongly in spermatocytes and mildly in oocytes, increasing the number of foci and intensity at the ends of spermatocyte chromosomes corresponding to visually elevated telomeric damage in the absence of SMC1β. This suggests the strong role of SMC1β in regulating TERRA at chromosome ends. TERRA, with a similar sequence to that of telomeres, has the potential to form RNA-DNA hybrids, often referred to as open R-loops, which may make telomeres more susceptible to damage. This study demonstrates that SMC1β-deficient mice exhibited increased staining for R-loops at both autosomal chromosome ends and sex chromosomes, which was mitigated upon treatment with RNase H endonuclease. In our recent publication, Biswas et al., 2023, it is confirmed that SMC1β helps maintain close chromatin at telomeric ends with support from ATAC sequencing and RNA sequencing data, thereby protecting the chromosome ends. One pertinent question that remains unanswered is what distinguishes SMC1β from SMC1α in maintaining these telomere functions. To address this, we generated a CRISPR-Cas9 mice strain with a deletion of the DNA binding domain at the carboxy terminal of SMC1β, which marks the major difference in sequence between SMC1β and SMC1α. While a reduced stability of these truncated proteins was observed at both RNA and protein levels in spermatocytes, yet it hints that the majority of SMC1β’s functions were abolished upon deletion of this C-tail. Interestingly, these mutant spermatocytes exhibit elevated telomere abnormalities, albeit not to the extent seen in full knockouts. This suggests that the C-terminal tail, along with additional components, participates in protecting telomeres, considering that a minimal level of SMC1β protein is sufficient to maintain telomeres in germ cells. Another objective of my thesis is to emphasize the significance of RAD21 as a kleisin protein in female meiosis. While there is limited research on RAD21 in spermatocytes, it has been described to transiently appear during late prophase I of male meiosis. However, studies on RAD21 in oocytes are lacking. RAD21 exhibits an appearance on the chromosome axis during mid to late pachytene in embryonic oocytes before being depleted in the diplotene stage. As RAD21 is the only kleisin protein in somatic cells, generating a constitutive Rad21 knockout mouse would be lethal. Therefore, using the Cre-LOX system, conditional Rad21 knockout mouse models were created, where RAD21 was specifically eliminated in oocytes at various stages of maturation. Early excision of Rad21 during the embryonic diplotene stage or in pups shortly after birth had a significant impact on ovary development and oocyte count with age, while oocyte sizes were reduced, indicating potential stress or onset of apoptosis. Conversely, late excision of Rad21 in activated germinal vesicle oocytes showed no notable differences in ovary size or oocyte number, and only mild differences in oocyte diameter, underscoring the significant role of RAD21 in the pre metaphase prophase stage. RAD21 does not actively participate in long-term arrest centromeric cohesin protection, chiasma maintenance, or DNA damage repair in heterozygous mice. However, young adult Rad21 conditional knockout mice with early excision exhibit a trend of delayed and less efficient oocyte maturation when exposed to DNA damage. These findings suggest a potential role of RAD21 in nonprogrammed DNA repair before metaphase I, which may ensure chromosome integrity after programmed recombination. Further investigation is necessary to study the mechanism of DNA repair by RAD21 through Homologous Recombination or End Joining pathways. In summary, these studies provide insights into the role of cohesin subunit SMC1β in telomere maintenance through TERRA regulation in spermatocytes, as well as the role of RAD21 in preserving ovarian reserve and oocyte health by potentially contributing to non-programmed DNA damage repair.