Variation in the TGF-β signaling pathway is emerging as an important mechanism by which gonadal sex determination is controlled in teleosts. Here we show that amhy, a Y-specific duplicate of the ...anti-Müllerian hormone (amh) gene, induces male sex determination in Nile tilapia. amhy is a tandem duplicate located immediately downstream of amhΔ-y on the Y chromosome. The coding sequence of amhy was identical to the X-linked amh (amh) except a missense SNP (C/T) which changes an amino acid (Ser/Leu92) in the N-terminal region. amhy lacks 5608 bp of promoter sequence that is found in the X-linked amh homolog. The amhΔ-y contains several insertions and deletions in the promoter region, and even a 5 bp insertion in exonVI that results in a premature stop codon and thus a truncated protein product lacking the TGF-β binding domain. Both amhy and amhΔ-y expression is restricted to XY gonads from 5 days after hatching (dah) onwards. CRISPR/Cas9 knockout of amhy in XY fish resulted in male to female sex reversal, while mutation of amhΔ-y alone could not. In contrast, overexpression of Amhy in XX fish, using a fosmid transgene that carries the amhy/amhΔ-y haplotype or a vector containing amhy ORF under the control of CMV promoter, resulted in female to male sex reversal, while overexpression of AmhΔ-y alone in XX fish could not. Knockout of the anti-Müllerian hormone receptor type II (amhrII) in XY fish also resulted in 100% complete male to female sex reversal. Taken together, these results strongly suggest that the duplicated amhy with a missense SNP is the candidate sex determining gene and amhy/amhrII signal is essential for male sex determination in Nile tilapia. These findings highlight the conserved roles of TGF-β signaling pathway in fish sex determination.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The cost of DNA sequencing continues to fall, which makes it feasible to develop genomic resources for new model species that are well suited for studying questions in evolutionary biology. The ...thousands of closely related cichlid fishes in the lakes of East Africa are an ideal model system for understanding the genetic basis of vertebrate speciation. Genomic techniques are helping to integrate empirical and theoretical studies by identifying the genes that underlie the phenotypic differences among species.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This report provides a comprehensive overview of the adverse effects of hyperglycemia on the periodontium. It combines data from literature reviews of original data from two large, population‐based ...epidemiologic studies with comprehensive periodontal health assessment. Emphasis is placed on the exploration of hitherto sparsely reported effects of prediabetes and poorly controlled (uncontrolled) diabetes, in contrast to the umbrella term “diabetes.” This stems from the realization that it is not simply having a diagnosis of diabetes that may adversely affect periodontal health. Rather, it is the level (severity) of hyperglycemia that is the determining factor, not the case definition of the diagnosis of diabetes or the type of diabetes in question. Importantly, based on existing evidence this paper also attempts to estimate the improvements in periodontal probing depth and clinical attachment level that can be expected upon successful nonsurgical periodontal treatment in people with chronic periodontitis, with and without diabetes, respectively. This exploration includes the implentation of new systematic reviews and meta‐analyses that allow comparison of such intervention outcomes between hyperglycemic and normoglycemic subjects. Based on both existing literature and original analyses of population‐based studies, we try to answer questions such as: Is there a glycated hemoglobin concentration threshold for periodontitis risk? Does short‐term periodontal probing depth reduction and clinical attachment level gain after scaling and root planing depend on glycemic control in type 2 diabetes? Are short‐term scaling and root planing outcomes in people with hyperglycemia/diabetes inferior to those in people without diabetes? Do periodontitis patients with diabetes benefit more from the use of adjuvant antibiotics with nonsurgical periodontal treatment than people without diabetes? Does hyperglycemia lead to greater tooth loss in patients in long‐term post‐periodontal treatment maintenance programs? Throughout this review, we compare our new findings with previous data and report whether the results of these new analyses corroborate, or are in discord with, similar scientific reports in the literature. We also explore the potential role of dental health‐care professionals in helping patients control the risk factors that are identical for periodontitis and diabetes. Finally, we suggest various topics that still need exploration in future research.
B chromosomes are extra, non-essential chromosomes present in addition to the normal complement of A chromosomes. Many species of cichlid fish in Lake Malawi carry a haploid, female-restricted B ...chromosome. Here we show that this B chromosome exhibits drive, with an average transmission rate of 70%. The offspring of B-transmitting females exhibit a strongly female-biased sex ratio. Genotyping of these offspring reveals the B chromosome carries a female sex determiner that is epistatically dominant to an XY system on linkage group 7. We suggest that this sex determiner evolved to enhance the meiotic drive of the B chromosome. This is some of the first evidence that female meiotic drive can lead to the invasion of new sex chromosomes solely to benefit the driver, and not to compensate for skewed sex ratios.
Tilapias are the second most farmed fishes in the world and a sustainable source of food. Like many other fish, tilapias are sexually dimorphic and sex is a commercially important trait in these ...fish. In this study, we developed a significantly improved assembly of the tilapia genome using the latest genome sequencing methods and show how it improves the characterization of two sex determination regions in two tilapia species.
A homozygous clonal XX female Nile tilapia (Oreochromis niloticus) was sequenced to 44X coverage using Pacific Biosciences (PacBio) SMRT sequencing. Dozens of candidate de novo assemblies were generated and an optimal assembly (contig NG50 of 3.3Mbp) was selected using principal component analysis of likelihood scores calculated from several paired-end sequencing libraries. Comparison of the new assembly to the previous O. niloticus genome assembly reveals that recently duplicated portions of the genome are now well represented. The overall number of genes in the new assembly increased by 27.3%, including a 67% increase in pseudogenes. The new tilapia genome assembly correctly represents two recent vasa gene duplication events that have been verified with BAC sequencing. At total of 146Mbp of additional transposable element sequence are now assembled, a large proportion of which are recent insertions. Large centromeric satellite repeats are assembled and annotated in cichlid fish for the first time. Finally, the new assembly identifies the long-range structure of both a ~9Mbp XY sex determination region on LG1 in O. niloticus, and a ~50Mbp WZ sex determination region on LG3 in the related species O. aureus.
This study highlights the use of long read sequencing to correctly assemble recent duplications and to characterize repeat-filled regions of the genome. The study serves as an example of the need for high quality genome assemblies and provides a framework for identifying sex determining genes in tilapia and related fish species.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
African cichlids display a remarkable assortment of jaw morphologies, pigmentation patterns, and mating behaviors. In addition to this previously documented diversity, recent studies have documented ...a rich diversity of sex chromosomes within these fishes. Here we review the known sex-determination network within vertebrates, and the extraordinary number of sex chromosomes systems segregating in African cichlids. We also propose a model for understanding the unusual number of sex chromosome systems within this clade.
Sex determination mechanisms differ among animal species, but it is not clear how these differences evolve. New sex determiners may arise in response to sexual conflicts, which occur when traits ...benefit one sex but hinder the other. We identified the genetic basis for the orange-blotch (OB) color pattern, a trait under sexually antagonistic selection in the cichlid fish of Lake Malawi, East Africa. The OB phenotype is due to a cis-regulatory mutation in the Pax7 gene. OB provides benefits of camouflage to females but disrupts the species-specific male color patterns used for mate recognition. We suggest that the resulting sexual conflict over the OB allele has been resolved by selection for a novel female sex determination locus that has invaded populations with an ancestral male sex determination system.
Abstract
Premelanosome protein (pmel) is a key gene for melanogenesis. Mutations in this gene are responsible for white plumage in chicken, but its role in pigmentation of fish remains to be ...demonstrated. In this study, we found that most fishes have 2 pmel genes arising from the teleost-specific whole-genome duplication. Both pmela and pmelb were expressed at high levels in the eyes and skin of Nile tilapia. We mutated both genes in tilapia using CRISPR/Cas9. Homozygous mutation of pmela resulted in yellowish body color with weak vertical bars and a hypopigmented retinal pigment epithelium (RPE) due to significantly reduced number and size of melanophores. In contrast, we observed an increased number and size of xanthophores in mutants compared to wild-type fish. Homozygous mutation of pmelb resulted in a similar, but milder phenotype than pmela−/− mutants. Double mutation of pmela and pmelb resulted in loss of additional melanophores compared to the pmela−/− mutants, and also an increase in the number and size of xanthophores, producing a golden body color. The RPE pigmentation of pmela−/−;pmelb−/− was similar to pmela−/− mutants, with much less pigmentation than pmelb−/− mutants and wild-type fish. Taken together, our results indicate that, although both pmel genes are important for the formation of body color in tilapia, pmela plays a more important role than pmelb. To our knowledge, this is the first report on mutation of pmelb or both pmela;pmelb in fish. Studies on these mutants suggest new strategies for breeding golden tilapia, and also provide a new model for studies of pmel function in vertebrates.
The impacts of androgens and glucocorticoids on spermatogenesis have intrigued scientists for decades. 11β-hydroxylase, encoded by cyp11c1, is the key enzyme involved in the synthesis of ...11-ketotestosterone and cortisol, the major androgen and glucocorticoid in fish, respectively. In the present study, a Cyp11c1 antibody was produced. Western blot and immunohistochemistry showed that Cyp11c1 was predominantly expressed in the testicular Leydig cells and head kidney interrenal cells. A mutant line of cyp11c1 was established by CRISPR/Cas9. Homozygous mutation of cyp11c1 caused a sharp decrease of serum cortisol and 11-ketotestosterone, and a delay in spermatogenesis which could be rescued by exogenous 11-ketotestosterone or testosterone, but not cortisol treatment. Intriguingly, this spermatogenesis restored spontaneously, indicating compensatory effects of other androgenic steroids. In addition, loss of Cyp11c1 led to undersized testes with a smaller efferent duct and disordered spermatogenic cysts in adult males. However, a small amount of viable sperm was produced. Taken together, our results demonstrate that cyp11c1 is important for testicular development, especially for the initiation and proper progression of spermatogenesis. 11-ketotestosterone is the most efficient androgen in tilapia.
Foxh1, a member of fox gene family, was first characterized as a transcriptional partner in the formation of the Smad protein complex. Recent studies have shown foxh1 is highly expressed in the ...cytoplasm of oocytes in both tilapia and mouse. However, its function in oogenesis remains unexplored. In the present study, foxh1–/– tilapia was created by CRISPR/Cas9. At 180 dah (days after hatching), the foxh1–/– XX fish showed oogenesis arrest and a significantly lower GSI. The transition of oocytes from phase II to phase III and follicle cells from one to two layers was blocked, resulting in infertility of the mutant. Transcriptomic analysis revealed that expression of genes involved in estrogen synthesis and oocyte growth were altered in the foxh1–/– ovaries. Loss of foxh1 resulted in significantly decreased Cyp19a1a and increased Cyp11b2 expression, consistent with significantly lower concentrations of serum estradiol-17β (E2) and higher concentrations of 11-ketotestosterone (11-KT). Moreover, administration of E2 rescued the phenotypes of foxh1–/– XX fish, as indicated by the appearance of phase III and IV oocytes and absence of Cyp11b2 expression. Taken together, these results suggest that foxh1 functions in the oocytes to regulate oogenesis by promoting cyp19a1a expression, and therefore estrogen production. Disruption of foxh1 may block the estrogen synthesis and oocyte growth, leading to the arrest of oogenesis and thus infertility in tilapia.
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