Early dorsomedial tissue interactions regulate gyrification of distal neocortex

The extent of neocortical gyrification is an important determinant of a species’ cognitive abilities, yet the mechanisms regulating cortical gyrification are poorly understood. We uncover long-range regulation of this process originating at the telencephalic dorsal midline, where levels of secreted Bmps are maintained by factors in both the neuroepithelium and the overlying mesenchyme. In the mouse, the combined loss of transcription factors Lmx1a and Lmx1b, selectively expressed in the midline neuroepithelium and the mesenchyme respectively, causes dorsal midline Bmp signaling to drop at early neural tube stages. This alters the spatial and temporal Wnt signaling profile of the dorsal midline cortical hem, which in turn causes gyrification of the distal neocortex. Our study uncovers early mesenchymal-neuroepithelial interactions that have long-range effects on neocortical gyrification and shows that lissencephaly in mice is actively maintained via redundant genetic regulation of dorsal midline development and signaling.

Larval development of the Mexican Snook, Centropomus poeyi (Teleostei: Centropomidae)

ABSTRACT We document for the first time the early ontogeny of Centropomus poeyi based on captive raised material representing 0-19 days posthatch (dph). The achievement of early developmental landmarks (i.e., yolk-sac depletion, flexion, development of fins) and changes in pigmentation are described (1.4 mm NL-10.6 mm SL; 0-19 dph) and documented for a subset of individuals using high quality photographs. The ontogeny of the viscerocranium is also described (2.4 mm NL-10.6 mm SL; 6-19 dph). Development in C. poeyi occurs over a short period with attainment of the juvenile stage (i.e., full complement of fin rays present in each fin) occurring by 6.9 mm SL. The ontogeny of external pigmentation in C. poeyi is marked by two trends throughout growth: (1) a decrease in pigmentation dorsally; and (2) an increase in pigmentation ventrally along the midline. Development of the viscerocranium begins with the appearance of the maxilla and dentary in individuals of 2.4 mm NL, coinciding with the depletion of the yolk-sac. By 10.6 mm SL all bones of the viscerocranium are present and teeth are present on all teeth-bearing bones of the adult. Aspects of early development in C. poeyi are compared with the congeners C. undecimalis and C. parallelus.

Sternal reconstruction by extracellular matrix: a rare case of phaces syndrome

Congenital defects of the sternum are rare and due to a failure of midline development and fusion of the sternal bones. Surgical correction of a sternal cleft should be preferred during infancy for functional reasons. Chest wall reconstruction represented a complex problem in the last decades.We report our successful outcome of sternal reconstruction in a rare case of PHACES syndrome, in which the patient was submitted to reconstruction of the sternum and complete closure of the thoracic defect by the employ of an extracellular matrix XCM Biologic tissue matrix.We promote the use of extracellular matrix in surgical reconstruction of chest defects for its maneuverability, plasticity, tolerability and the possibility of growing with the children’s chest getting a good compliance and optimal cosmetic results.

Targeted Gene Knockdown in Zebrafish Reveals Distinct Intraembryonic Functions for Insulin-Like Growth Factor II Signaling

IGF-II is the predominant IGF ligand regulating prenatal growth in all vertebrates, including humans, but its central role in placental development has confounded efforts to fully elucidate its functions within the embryo. Here we use a nonplacental model vertebrate (zebrafish) to interrogate the intraembryonic functions of IGF-II signaling. The zebrafish genome contains two coorthologs of mammalian IGF2 (igf2a, igf2b), which exhibit distinct patterns of expression during embryogenesis. Expression of igf2a mRNA is restricted to the notochord, primarily during segmentation/neurulation. By contrast, igf2b mRNA is expressed in midline tissues adjacent to the notochord, with additional sites of expression in the ventral forebrain, and the pronephros. To identify their intraembryonic functions, we suppressed the expression of each gene with morpholino oligonucleotides. Knockdown of igf2a led to defects in dorsal midline development, characterized by delayed segmentation, notochord undulations, and ventral curvature. Similarly, suppression of igf2b led to defects in dorsal midline development but also induced ectopic fusion of the nephron primordia, and defects in ventral forebrain development. Subsequent onset of severe body edema in igf2b, but not igf2a morphants, further suggested a distinct role for igf2b in development of the embryonic kidney. Simultaneous knockdown of both genes increased the severity of dorsal midline defects, confirming a conserved role for both genes in dorsal midline development. Collectively, these data provide evidence that the zebrafish orthologs of IGF2 function in dorsal midline development during segmentation/neurulation, whereas one paralog, igf2b, has evolved additional, distinct functions during subsequent organogenesis.