The International Journal of Developmental Biology

ABSTRACT

The nucleocytoplasmic translocation of yes-associated protein 1 (YAP1) controls the growth of animal tissues and organs. YAP1 binds to transcription factors in the nucleus to activate the transcription of proliferation and anti-apoptotic genes. The Hippo pathway prevents the nuclear translocation of YAP1 by phosphorylating YAP1, while mechanical forces promote it by opening the nuclear pore complex and stimulating other signaling pathways. Recently we found that Protein salvador homolog 1 (SAV1), a component of the Hippo pathway, interacts with filamin A (FLNA) in a force-dependent manner, raising a possibility that the Hippo pathway is regulated by mechanical force through the FLNA-SAV1 axis. To test this hypothesis, we generated conditional knock-in (KI) mice expressing non-Flna-binding mutant Sav1 in hepatocytes by crossing with mice carrying Cre recombinase driven by the serum albumin (alb) gene promoter. Unexpectedly, the insertion of the flox cassette skipped exon 2, resulting in a shorter Sav1 in all the transgenic mice. Since exon 2 encodes a fragment containing a Flna-binding domain, we analyzed both point mutant KI and exon 2-deleted mutant mice. Here we show that...

ABSTRACT

Biotechniques, including surrogate propagation derived from primordial germ cell (PGC) transplantation, are valuable tools for the reconstitution of endangered fish species. Although promising, there are no previous studies reporting such approaches using neotropical fish species. The aim of this study was to establish germline chimeras in neotropical fish by using the yellowtail tetra Astyanax altiparanae as a model species of the order Characiformes. Germline chimeras were obtained after transplantation of PGCs cultivated under different conditions: saline medium and supplemented with DMEM, amino acids, vitamins, glutamine, pyruvate, and fetal bovine serum, and subsequently transplanted into A. altiparanae triploids and triploid hybrids from the cross between A. altiparanae (♀) and A. fasciatus (♂). The results indicate ectopic migration in host embryos after transplantation of PGCs cultivated in saline medium. However, PGCs cultivated in supplemented medium migrated to the region of the gonadal ridge in 4.5% of triploid and 19.3% in triploid hybrid. In addition, the higher expression of dnd1, ddx4 and dazl genes was...

ABSTRACT

The gene KIAA0319-Like (KIAA0319L) is thought to confer susceptibility for developmental dyslexia. Dyslexia may be caused by alterations in neuronal migration, and in utero knockdown of KIAA0319L in rats indicated migration errors. However, studies carried out with KIAA0319L knockout mice did not reveal an altered neuronal migration phenotype. Gene knockout may activate compensatory mechanisms to buffer against genetic mutations during development. Here we assessed the role of KIAA0319L on migrating neurons in the chick developing tectum. Whole mount in situ hybridization was performed for KIAA0319L on embryonic day (E)3 – E5 chick embryos and in situ hybridization on sections was performed at later stages. The specificity and efficiency of engineered microRNA (miRNA) constructs targeting KIAA0319L for knocking down KIAA0319L were verified. miRNAs were electroporated into E5 chick optic tecta. Our studies demonstrate that KIAA0319L is expressed in the developing chick visual system, as well as in the otic vesicles. Knockdown of KIAA0319L in the optic tectum results in abnormal neuronal migration, strengthening the argument that KIAA0319L is involved in this developmental process.

ABSTRACT

All tetrapods (mammals, birds, reptiles, and amphibians) share the ability to breathe with their mouths closed due to the formation of choanae, which are openings that allow communication between the nasal and oral cavities. In most fishes, the nasal cavities serve a strictly olfactory function, possessing incurrent and excurrent nares that lie outside of the mouth and therefore, never communicate with the respiratory system. It is not until the evolution of tetrapods, in which the nasal cavities consistently open into the mouth, that they are used both for olfaction and for respiration. However, this developmental transition is poorly understood, with no consensus on the evolutionary origin of the choana in various groups despite decades of debate. Here, we use high-contrast 3D imaging in conjunction with histology and apoptotic cell analysis in non-mineralized embryonic tissues to study the formation of the choana in the axolotl (Ambystoma mexicanum), an aquatic salamander species. We show that the axolotl choana forms from an extension of the embryonic nasal sac, which pushes through intervening mesenchyme and connects with the palate epithelium of the oral cavity,...