Hindbrain development and evolution: past, present, and future

Chiari Malformation Type III: A Case Report and Review of Literature

Chiari malformations (CMs) are a group of disorders involving deformities of the posterior fossa and hindbrain. There are seven types of CMs: 0, I, 1.5, II, III, IV, and V. CMIII is a very infrequent disorder characterized by low occipital or superior cervical encephalocele and inferior displacement of the brainstem. Here we present a unique case of CMIII associated with cleft palate, abnormal midbrain, and abnormal corpus callosum. CMIII is a very rare condition, which needs to be reported. This study primarily aims to compare our case to other cases of CMIII. We did not find another case with cleft palate and CMIII. There are only a few cases reported of CMIII. That is why it is vital to report each of these cases. Among reported CMIII cases, our case is unique regarding the co-occurrence of cleft palate. There seems to be an embryological link between these two conditions. However, cleft palate is a relatively common congenital defect, which means that the co-occurrence could be just a coincidence as well. Further research is warranted to broaden the information of this extremely rare syndrome.

Watching the assembly of an organ a single cell at a time using confocal multi-position photoactivation and multi-time acquisition

Tracing cell movements in vivo yields important clues to organogenesis, yet it has been challenging to accurately and reproducibly fluorescently mark single and small groups of cells to build a picture of tissue assembly. In the early embryo, the small size (hundreds of cells) of progenitor cell regions has made it easier to identify and selectively mark superficially located cells by glass needle injection. However,during early organogenesis,subregions of interest may be several millions of cells in volume located deeper within the embryo requiring an alternative approach. Here, we combined (confocal and 2-photon) photoactivation cell labeling and multi-position, multi-time imaging to trace single cell and small subgroups of cells in the developing brain and spinal cord. We compared the photostability and photoefficiency of a photoswitchable fluorescent protein, PSCFP2, with a novel nuclear localized H2B-PSCFP2 protein. We showed that both fluorescent proteins have similar photophysical properties and H2B-PSCFP2 is more effective in single cell identification in dense tissue. To accurately and reproducibly fluorescently trace subregions of cells in a 3D tissue volume, we developed a protocol for multi-position photoactivation and multi-time acquisition in the chick spinal cord in up to eight tissue sections. We applied our techniques to address the formation of the sympathetic ganglia,a major component of the autonomic nervous system,and showed there are phenotypic differences between early and later emerging neural crest cells and their positions in the developing ganglia. Thus, targeted fluorescent cell marking by confocal or 2-photon multi-position photoactivation and multi-time acquisition offer a more efficient, less invasive technique to trace cell movements in large regions of interest and move us closer towards mapping the cellular events of organogenesis.