No abstract

Alternative splicing (AS) is common in higher eukaryotes and plays an important role in gene posttranscriptional regulation. It has been suggested that AS varies dramatically among species, tissues, and duplicated gene families of different sizes. However, the genomic forces that govern AS variation remain poorly understood. Here, through genome-wide identification of AS events in the soybean (Glycine max) genome using high-throughput RNA sequencing of 28 samples from different developmental stages, we found that more than 63% of multiexonic genes underwent AS. More AS events occurred in the younger developmental stages than in the older developmental stages for the same type of tissue, and the four main AS types, exon skipping, intron retention, alternative donor sites, and alternative acceptor sites, exhibited different characteristics. Global computational analysis demonstrated that the variations of AS frequency and AS types were significantly correlated with the changes of gene features and gene transcriptional level. Further investigation suggested that the decrease of AS within the genome-wide duplicated genes were due to the diminution of intron length, exon number, and transcriptional level. Altogether, our study revealed that a large number of genes were alternatively spliced in the soybean genome and that variations in gene structure and transcriptional level may play important roles in regulating AS.

Sperm motility is vital to human reproduction. Malformations of sperm flagella can cause male infertility. Men with multiple morphological abnormalities of the flagella (MMAF) have abnormal spermatozoa with absent, short, coiled, bent, and/or irregular-caliber flagella, which impair sperm motility. The known human MMAF-associated genes, such as DNAH1, only account for fewer than 45% of affected individuals. Pathogenic mechanisms in the genetically unexplained MMAF remain to be elucidated. Here, we conducted genetic analyses by using whole-exome sequencing and genome-wide comparative genomic hybridization microarrays in a multi-center cohort of 30 Han Chinese men affected by MMAF. Among them, 12 subjects could not be genetically explained by any known MMAFassociated genes. Intriguingly, we identified compound-heterozygous mutations in CFAP43 in three subjects and a homozygous frameshift mutation in CFAP44 in one subject. All of these recessive mutations were parentally inherited from heterozygous carriers but were absent in 984 individuals from three Han Chinese control populations. CFAP43 and CFAP44, encoding two cilia-and flagella-associated proteins (CFAPs), are specifically or preferentially expressed in the testis. Using CRISPR/Cas9 technology, we generated two knockout models each deficient in mouse ortholog Cfap43 or Cfap44. Notably, both Cfap43-and Cfap44-deficient male mice presented with MMAF phenotypes, whereas the corresponding female mice were fertile. Our experimental observations on human subjects and animal models strongly suggest that biallelic mutations in either CFAP43 or CFAP44 can cause sperm flagellar abnormalities and impair sperm motility. Further investigations on other CFAP-encoding genes in more genetically unexplained MMAF-affected individuals could uncover novel mechanisms underlying sperm flagellar formation.