BackgroundChina is in the process of integrating the new cooperative medical scheme (NCMS) and the urban residents’ basic medical insurance system (URBMI) into the urban and rural residents’ basic medical insurance system (URRBMI). However, how to integrate the financing policies of NCMS and URBMI has not been described in detail. This paper attempts to illustrate the differences between the financing mechanisms of NCMS and URBMI, to analyze financing inequity between urban and rural residents and to identify financing mechanisms for integrating urban and rural residents’ medical insurance systems.MethodsFinancing data for NCMS and URBMI (from 2008 to 2015) was collected from the China health statistics yearbook, the China health and family planning statistics yearbook, the National Handbook of NCMS Information, the China human resources and social security statistics yearbook, and the China social security yearbook. “Ability to pay” was introduced to measure inequity in health financing. Individual contributions to NCMS and URBMI as a function of per capita disposable income was used to analyze equity in health financing between rural and urban residents.ResultsURBMI had a financing mechanism that was similar to that used by NCMS in that public finance accounted for more than three quarters of the pooling funds. The scale of financing for NCMS was less than 5% of the per capita net income of rural residents and less than 2% of the per capita disposable income of urban residents for URBMI. Individual contributions to the NCMS and URBMI funds were less than 1% of their disposable and net incomes. Inequity in health financing between urban and rural residents in China was not improved as expected with the introduction of NCMS and URBMI. The role of the central government and local governments in financing NCMS and URBMI was oscillating in the past decade.ConclusionsThe scale of financing for URRBMI is insufficient for the increasing demands for medical services from the insured. The pooling fund should be increased so that it can better adjust to China’s rapidly aging population and epidemiological transitions as well as protect the insured from poverty due to illness. Individual contributions to the URBMI and NCMS funds were small in terms of contributors’ incomes. The role of the central government and local governments in financing URRBMI was not clearly identified. Individual contributions to the URRBMI fund should be increased to ensure the sustainable development of URRBMI. Compulsory enrollment should be required so that URRBMI improves the social medical insurance system in China.
Evolutionary fates of duplicated genes have been widely investigated in many polyploid plants and animals, but research is scarce in recurrent polyploids. In this study, we focused on foxl2, a central player in ovary, and elaborated the functional divergence in gibel carp (Carassius gibelio), a recurrent auto-allo-hexaploid fish. First, we identified three divergent foxl2 homeologs (Cgfoxl2a-B, Cgfoxl2b-A, and Cgfoxl2b-B), each of them possessing three highly conserved alleles and revealed their biased retention/loss. Then, their abundant sexual dimorphism and biased expression were uncovered in hypothalamic–pituitary–gonadal axis. Significantly, granulosa cells and three subpopulations of thecal cells were distinguished by cellular localization of CgFoxl2a and CgFoxl2b, and the functional roles and the involved process were traced in folliculogenesis. Finally, we successfully edited multiple foxl2 homeologs and/or alleles by using CRISPR/Cas9. Cgfoxl2a-B deficiency led to ovary development arrest or complete sex reversal, whereas complete disruption of Cgfoxl2b-A and Cgfoxl2b-B resulted in the depletion of germ cells. Taken together, the detailed cellular localization and functional differences indicate that Cgfoxl2a and Cgfoxl2b have subfunctionalized and cooperated to regulate folliculogenesis and gonad differentiation, and Cgfoxl2b has evolved a new function in oogenesis. Therefore, the current study provides a typical case of homeolog/allele diversification, retention/loss, biased expression, and sub-/neofunctionalization in the evolution of duplicated genes driven by polyploidy and subsequent diploidization from the recurrent polyploid fish.
Triploids are rare in nature because of difficulties in meiotic and gametogenic processes, especially in vertebrates. The Carassius complex of cyprinid teleosts contains sexual tetraploid crucian carp/goldfish (C. auratus) and unisexual hexaploid gibel carp/Prussian carp (C. gibelio) lineages, providing a valuable model for studying the evolution and maintenance mechanism of unisexual polyploids in vertebrates. Here we sequence the genomes of the two species and assemble their haplotypes, which contain two subgenomes (A and B), to the chromosome level. Sequencing coverage analysis reveals that C. gibelio is an amphitriploid (AAABBB) with two triploid sets of chromosomes; each set is derived from a different ancestor. Resequencing data from different strains of C. gibelio show that unisexual reproduction has been maintained for over 0.82 million years. Comparative genomics show intensive expansion and alterations of meiotic cell cycle-related genes and an oocyte-specific histone variant. Cytological assays indicate that C. gibelio produces unreduced oocytes by an alternative ameiotic pathway; however, sporadic homologous recombination and a high rate of gene conversion also exist in C. gibelio. These genomic changes might have facilitated purging deleterious mutations and maintaining genome stability in this unisexual amphitriploid fish. Overall, the current results provide novel insights into the evolutionary mechanisms of the reproductive success in unisexual polyploid vertebrates.
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