ABSTRACT
Satellite DNA (satDNA) consists of sequences of DNA that form tandem repetitions across the genome, and it is notorious for its diversity and fast evolutionary rate. Despite its importance, satDNA has been only sporadically studied in reptile lineages. Here, we sequenced genomic DNA and PCR-amplified microdissected W chromosomes on the Illumina platform in order to characterize the monomers of satDNA from the Henkel's leaf-tailed gecko U. henkeli and to compare their topology by in situ hybridization in the karyotypes of the closely related Günther's flat-tail gecko U. guentheri and gold dust day gecko P. laticauda. We identified seventeen different satDNAs; twelve of them seem to accumulate in centromeres, telomeres and/or the W chromosome. Notably, centromeric and telomeric regions seem to share similar types of satDNAs, and we found two that seem to accumulate at both edges of all chromosomes in all three species. We speculate that the long-term stability of all-acrocentric karyotypes in geckos might be explained from the presence of specific satDNAs at the centromeric regions that are strong meiotic drivers, a hypothesis that should be further tested.
Subject(s)
Centromere , Cytogenetic Analysis , DNA, Satellite , Karyotype , Lizards , Telomere , Animals , Lizards/genetics , Centromere/genetics , DNA, Satellite/genetics , Telomere/genetics , Cytogenetic Analysis/methods , In Situ Hybridization, FluorescenceABSTRACT
Geckos are an excellent group to study the evolution of sex determination, as they possess a remarkable variability ranging from a complete absence of sex chromosomes to highly differentiated sex chromosomes. We explored sex determination in the Madagascar leaf-tail geckos of the genus Uroplatus. The cytogenetic analyses revealed highly heterochromatic W chromosomes in all three examined species (Uroplatus henkeli, U. alluaudi, U. sikorae). The comparative gene coverage analysis between sexes in U. henkeli uncovered an extensive Z-specific region, with a gene content shared with the chicken chromosomes 8, 20, 26 and 28. The genomic region homologous to chicken chromosome 28 has been independently co-opted for the role of sex chromosomes in several vertebrate lineages, including monitors, beaded lizards and monotremes, perhaps because it contains the amh gene, whose homologs were repeatedly recruited as a sex-determining locus. We demonstrate that all tested species of leaf-tail geckos share homologous sex chromosomes despite the differences in shape and size of their W chromosomes, which are not homologous to the sex chromosomes of other closely related genera. The rather old (at least 40 million years), highly differentiated sex chromosomes of Uroplatus geckos can serve as a great system to study the convergence of sex chromosomes evolved from the same genomic region.
Subject(s)
Lizards , Animals , Lizards/genetics , Phylogeny , Madagascar , Sex Chromosomes/geneticsABSTRACT
Geckos (Gekkota), the species-rich clade of reptiles with more than 2200 currently recognized species, demonstrate a remarkable variability in diploid chromosome numbers (2n = 16-48) and mode of sex determination. However, only a small fraction of gekkotan species have been studied with cytogenetic methods. Here, we applied both conventional (karyotype reconstruction and C-banding) and molecular (fluorescence in situ hybridization with probes for rDNA loci and telomeric repeats) cytogenetic analyses in seven species of geckos, namely Blaesodactylus boivini, Chondrodactylus laevigatus, Gekko badenii, Gekko cf. lionotum, Hemidactylus sahgali, Homopholis wahlbergii (Gekkonidae) and Ptyodactylus togoensis (Phyllodactylidae), in order to provide further insights into the evolution of karyotypes in geckos. Our analysis revealed the presence of interstitial telomeric repeats in four species, but we were not able to conclude if they are remnants of previous chromosome rearrangements or were formed by an accumulation of telomeric-like satellite motifs. Even though sex chromosomes were previously identified in several species from the genera Hemidactylus and Gekko by cytogenetic and/or genomic methods, they were not detected by us in any examined species. Our examined species either have poorly differentiated sex chromosomes or, possibly, environmental sex determination. Future studies should explore the effect of temperature and conduct genome-wide analyses in order to identify the mode of sex determination in these species.
Subject(s)
Lizards , Animals , Lizards/genetics , In Situ Hybridization, Fluorescence , Genome-Wide Association Study , Sex Chromosomes/genetics , KaryotypingABSTRACT
This study aimed to evaluate changes in beige adipocytes at different times of melatonin administration, in the morning (ZT01) or in the evening (ZT11), at 30 mg/kg daily by gavage for 7 weeks or continuously with drinking water in the term of high-calorie diet-induced obesity (HCD). Melatonin received at ZT11 or with drinking water resulted in an increased area of the browning zone in the subcutaneous white adipose tissue (sWAT), even in rats with HCD (compared with Control or HCD, respectively). The beige adipocyte and lipid droplet area after melatonin use were reduced compared to those with HCD and Control, in all administration modes (group ZT01 showed smaller changes compared to ZT11 or with drinking water groups). The fibrosis level decreased and significantly differed in HCD ZT01, HCD ZT11, and HCD water compared to that in HCD; moreover, the lowest value determined in HCD water, reached the control parameters. Furthermore, the IL-1b and IL-8 level was decreased in the HCD groups under melatonin treatment at ZT11 or with drinking water compared to that in HCD. The obtained results suggest that melatonin promotes sWAT browning in rats with diet-induced obesity and influences morphological signs of normal rats depending on the time of administration. Different functional activity of beige adipocytes was observed after melatonin was used depending on the time of administration, resulting in heat production and lipolysis (the relative mass of visceral fat was likewise diminished). More rapid browning was observed when melatonin treatment was performed at 1 h before lights-off (ZT11) or continuously via drinking water. Melatonin acted on beige adipocytes of obese rats through changing some parameters such as the area of adipocytes and lipid drops, the number of lipid drops, the relative area browning of sWAT, and the level of tissue fibrosis.
Este estudio tuvo como objetivo evaluar los cambios en los adipocitos beige en diferentes momentos de la administración de melatonina, en la mañana (ZT01) o por la noche (ZT11). Se administraron 30 mg/kg diariamente por sonda durante 7 semanas o continuamente con agua potable durante el periodo de obesidad inducida por una dieta alta en calorías (HCD). La melatonina recibida en ZT11 o con agua potable resultó en un aumento de área dorada en tejido adiposo blanco subcutáneo (sWAT), incluso en ratas con HCD (en comparación con Control o HCD, respectivamente). El área de gotas de lípidos y adipocitos de color beige después del uso de melatonina se redujo en comparación con aquellos con HCD y Control, en todos los modos de administración (el grupo ZT01 mostró cambios más pequeños en comparación con ZT11 o con grupos de agua potable). El nivel de fibrosis disminuyó y difirió significativamente en HCD ZT01, HCD ZT11 y agua HCD, en comparación con el HCD; además, el valor más bajo determinado en agua HCD alcanzó los parámetros de control. Además, el nivel de IL-1b e IL-8 disminuyó en los grupos HCD bajo tratamiento con melatonina en ZT11 o con agua potable en comparación con el de HCD. Los resultados obtenidos sugieren que la melatonina promueve el dorado sWAT en ratas con obesidad inducida por la dieta e influye en los signos morfológicos de las ratas normales dependiendo del momento de la administración. Se observó una actividad funcional diferente de los adipocitos de color beige después de usar melatonina dependiendo del tiempo de administración, dando como resultado la producción de calor y lipólisis (la masa relativa de grasa visceral también disminuyó). Se observó un ennegrecimiento más rápido cuando el tratamiento con melatonina se realizó 1 h antes de apagar las luces (ZT11) o de forma continua en grupos de agua potable. La melatonina actuó en los adipocitos beige de ratas obesas al cambiar algunos parámetros, como el área de adipocitos y gotas de lípidos, el número de gotas de lípidos, el área relativa de ennegrecimiento de sWAT y el nivel de fibrosis tisular.
