Common dysmorphic oocytes and embryos in assisted reproductive technology laboratory in association with gene alternations

Amorphic or defected oocytes and embryos are commonly observed in assisted reproductive technology (ART) laboratories. It is believed that a proper gene expression at each stage of embryo development contributes to the possibility of a decent-quality embryo leading to successful implantation. Many studies reported that several defects in embryo morphology are associated with gene expressions during in vitro fertilization (IVF) treatment. There is lacking literature review on summarizing common morphological defects about gene alternations. In this review, we summarized the current literature. We selected 64 genes that have been reported to be involved in embryo morphological abnormalities in animals and humans, 30 of which were identified in humans and might be the causes of embryonic changes. Five papers focusing on associations of multiple gene expressions and embryo abnormalities using RNA transcriptomes were also included during the search. We have also reviewed our time-lapse image database with over 3000 oocytes/embryos to show morphological defects possibly related to gene alternations reported previously in the literature. This holistic review can better understand the associations between gene alternations and morphological changes. It is also beneficial to select important biomarkers with strong evidence in IVF practice and reveal their potential application in embryo selection. Also, identifying genes may help patients with genetic disorders avoid unnecessary treatments by providing preimplantation genetic testing for monogenic/single gene defects (PGT-M), reduce embryo replacements by less potential, and help scientists develop new methods for oocyte/embryo research in the near future.

RNAi for chitin synthase 1 rather than 2 causes growth delay and molting defect in Henosepilachna vigintioctopunctata

Chitin synthase (CHS) plays a critical role in chitin synthesis and excretion. In most insects, CHSs have been segregated into 1 and 2 classes. CHS1 is responsible for chitin production in the ectodermally-derived epidermal cells. CHS2 is dedicated to chitin biosynthesis in the midgut peritrophic matrix (PM). Henosepilachna vigintioctopunctata is a serious pest of Solanaceae and Cucurbitaceae plants. In this study, we identified HvCHS1 and HvCHS2. We found that HvCHS1 was abundantly transcribed in the larval tracheae and epidermis, whereas HvCHS2 was mainly expressed in the guts. Escherichia coli HT115 expressed double stranded RNAs targeting HvCHS1 and HvCHS2 (dsCHS1 and dsCHS2) were used to immerse potato foliage and the treated leaves were provided to the newly-molted fourth- and third-instar larvae. Ingestion of dsCHS1 by the fourth-instar larvae significantly diminished the target mRNA level and had slight influence on the expression of HvCHS2. In contrast, consumption of dsCHS2 significantly lowered the target mRNA level but triggered the transcription of HvCHS1. Knockdown of HvCHS1, rather than HvCHS2, arrested larval development and impaired larva-pupa-adult transition. A large proportion of HvCHS1 hypomorphs became stunting prepupae, deformed pupae or misshapen adults. Moreover, knockdown of HvCHS1 damaged gut integrity, decreased cuticle thickness, and delayed the formation of newly-generated cuticle layer during ecdysis. Furthermore, depletion of HvCHS1 inhibited the development of trachea system and thinned tracheal taenidia. Ingestion of dsCHS1 at the third-instar stage caused similar but severe negative effects. Our results demonstrated that HvCHS1 is responsible for chitin biosynthesis during ecdysis. Moreover, HvCHS1 is a potential amenable target gene and young larvae are more susceptible to dsRNA.