Trinucleotide repeat containing 6c (TNRC6c) is essential for microvascular maturation during distal airspace sacculation in the developing lung

Argonaute1 and Gawky Are Required for the Development and Reproduction of Melon fly, Zeugodacus cucurbitae

Argonaute family genes encode a highly conserved group of proteins that have been associated with RNA silencing in both animals and plants. This study investigates the importance of microRNA biogenesis key regulators Argonaute1 (Ago1) and Gawky genes in the post-embryonic and ovarian development of the melon fly, Zeugodacus cucurbitae. The expression levels of these genes were mapped in all developmental stages and different adult tissues. Their roles in development were investigated using RNA interference (RNAi) via two different dsRNA delivery techniques. Embryo microinjection and oral feeding of third instar larvae successfully knocked down and greatly reduced the expression level of the target genes. Additionally, ex vivo essays revealed the stability of dsRNA in food was sufficient for gene silencing, although its integrity was affected in midgut. A wide range of phenotypes were observed on pupation, segmentation, pigmentation, and ovarian development. RNAi-mediated silencing of Gawky caused high mortality and loss of body segmentation, while Ago1 knockdown affected ovarian development and pigmentation. Developmental abnormalities and ovarian malformations caused by silencing these genes suggest that these genes are crucial for viability and reproductive capacity of Z. cucurbitae, and may be used as potential target genes in pest management.

Massively parallel reporter assays discover de novo exonic splicing mutants in paralogs of Autism genes

To determine the contribution of defective splicing in Autism Spectrum Disorders (ASD), the most common neurodevelopmental disorder, a high throughput Massively Parallel Splicing Assay (MaPSY) was employed and identified 42 exonic splicing mutants out of 725 coding de novo variants discovered in the sequencing of ASD families. A redesign of the minigene constructs in MaPSY revealed that upstream exons with strong 5' splice sites increase the magnitude of skipping phenotypes observed in downstream exons. Select hits were validated by RT-PCR and amplicon sequencing in patient cell lines. Exonic splicing mutants were enriched in probands relative to unaffected siblings -especially synonymous variants (7.5% vs 3.5%, respectively). Of the 26 genes disrupted by exonic splicing mutations, 6 were in known ASD genes and 3 were in paralogs of known ASD genes. Of particular interest was a synonymous variant in TNRC6C - an ASD gene paralog with interactions with other ASD genes. Clinical records of 3 ASD patients with TNRC6C variant revealed respiratory issues consistent with phenotypes observed in TNRC6 depleted mice. Overall, this study highlights the need for splicing analysis in determining variant pathogenicity, especially as it relates to ASD.

Conserved mammalian modularity of quantitative trait loci revealed human functional orthologs in blood pressure control

Genome-wide association studies (GWAS) have routinely detected human quantitative trait loci (QTLs) for complex traits. Viewing that most GWAS single nucleotide polymorphisms (SNPs) are found in non-coding regions unrelated to the physiology of a polygenic trait of interest, a vital question to answer is whether or not any of these SNPs can functionally alter the phenotype with which it is associated. The study of blood pressure (BP) is a case in point. Conserved mechanisms in controlling BP by modularity is now unifying differing mammalian orders in that understanding mechanisms in rodents is tantamount to revealing the same in humans, while overcoming experimental limitations imposed by human studies. As a proof of principle, we used BP QTLs from Dahl salt-sensitive rats (DSS) as substitutes to capture distinct human functional orthologs. 3 DSS BP QTLs are located into distinct genome regions and correspond to several human GWAS genes. Each of the QTLs independently exerted a major impact on BP in vivo. BP was functionally changed by normotensive alleles from each of these QTLs, and yet, the human GWAS SNPs do not exist in the rat. They cannot be responsible for physiological alterations in BP caused by these QTLs. These SNPs are genome emblems for QTLs nearby, rather than being QTLs per se, since they only emerged during primate evolution after BP-regulating mechanisms have been established. We then identified specific mutated coding domains that are conserved between rodents and humans and that may implicate different steps of a common pathway or separate pathways.

Mark1 regulates distal airspace expansion through type I pneumocyte flattening in lung development

During the later stages of lung development, two types of pneumocytes, cuboidal type II (AECII) and flattened type I (AECI) alveolar epithelial cells, form distal lung saccules. Here, we highlight how fibroblasts expressing MAP-microtubule affinity regulating kinase 1 (Mark1) are required for the terminal stages of pulmonary development, called lung sacculation. In Mark1-knockout (KO) mice, distal sacculation and AECI flattening are significantly impaired. Fetal epithelial cells generate alveolar organoids and differentiate into pneumocytes when co-cultured with fibroblasts. However, the size of organoids decreased and AECI flattening was impaired in the presence of Mark1 KO fibroblasts. In Mark1 KO fibroblasts themselves, cilia formation and the Hedgehog pathway were suppressed, resulting in the loss of type I collagen expression. The addition of type I collagen restored AECI flattening in organoids co-cultured with Mark1 KO fibroblasts and rescued the decreased size of organoids. Mathematical modeling of distal lung sacculation supports the view that AECI flattening is necessary for the proper formation of saccule-like structures. These results suggest that Mark1-mediated fibroblast activation induces AECI flattening and thereby regulates distal lung sacculation.

Dysregulated Translation in Neurodevelopmental Disorders: An Overview of Autism-Risk Genes Involved in Translation

Regulated local translation-whereby specific mRNAs are transported and localized in subcellular domains where they are translated in response to regional signals-allows for remote control of gene expression to concentrate proteins in subcellular compartments. Neurons are highly polarized cells with unique features favoring local control for axonal pathfinding and synaptic plasticity, which are key processes involved in constructing functional circuits in the developing brain. Neurodevelopmental disorders are caused by genetic or environmental factors that disturb the nervous system's development during prenatal and early childhood periods. The growing list of genetic mutations that affect mRNA translation raises the question of whether aberrant translatomes in individuals with neurodevelopmental disorders share common molecular features underlying their stereotypical phenotypes and, vice versa, cause a certain degree of phenotypic heterogeneity. Here, we briefly give an overview of the role of local translation during neuronal development. We take the autism-risk gene list and discuss the molecules that (perhaps) are involved in mRNA transport and translation. Both exaggerated and suppressed translation caused by mutations in those genes have been identified or suggested. Finally, we discuss some proof-of-principle regimens for use in autism mouse models to correct dysregulated translation.

Long-Term Engraftment Promotes Differentiation of Alveolar Epithelial Cells from Human Embryonic Stem Cell Derived Lung Organoids

Human embryonic stem cell (hESC) derived 3D human lung organoids (HLOs) provide a promising model to study human lung development and disease. HLOs containing proximal or/and immature distal airway epithelial cells have been successfully generated in vitro, such as early staged alveolar type 2 (AT2) cells (SPC⁺/SOX9⁺) and immature alveolar type 1 (AT1) cells (HOPX⁺/SOX9⁺). When HLOs were transplanted into immunocompromised mice for further differentiation in vivo, only few distal epithelial cells could be observed. In this study, we transplanted different stages of HLOs into immunocompromised mice to assess whether HLOs could expand and mature in vivo. We found that short-term transplanted HLOs contained lung progenitor cells (NKX2.1⁺, SOX9⁺, and P63⁺), but not SPC⁺ AT2 cells or AQP5⁺ AT1 cells. Meanwhile, long-term engrafted HLOs could differentiate into lung distal bipotent progenitor cells (PDPN⁺/SPC⁺/SOX9⁺), AT2 cells (SPC⁺, SPB⁺), and immature AT1 cells (PDPN⁺, AQP5^-). However, HLOs at late in vitro stage turned into mature AT1-like cells (AQP5⁺/SPB^-/SOX9^-) in vivo. Immunofluorescence staining and transmission electron microscopy (TEM) results revealed that transplanted HLOs contained mesenchymal cells (collagen I⁺), vasculature (ACTA2⁺), neuroendocrine-like cells (PGP9.5⁺), and nerve fiber structures (myelin sheath structure). Together, these data reveal that hESC-derived HLOs would be useful for human lung development modeling, and transplanted HLOs could mimic lung organ-like structures in vivo by possessing vascular network and neuronal network.