Incipient forebrain boundaries traced by differential gene expression and fate mapping in the chick neural plate

We correlated available fate maps for the avian neural plate at stages HH4 and HH8 with the progress of local molecular specification, aiming to determine when the molecular specification maps of the primary longitudinal and transversal domains of the anterior forebrain agree with the fate mapped data. To this end, we examined selected gene expression patterns as they normally evolved in whole mounts and sections between HH4 and HH8 (or HH10/11 in some cases), performed novel fate-mapping experiments within the anterior forebrain at HH4 and examined the results at HH8, and correlated grafts with expression of selected gene markers. The data provided new details to the HH4 fate map, and disclosed some genes (e.g., Six3 and Ganf) whose expression domains initially are very extensive and subsequently retract rostralwards. Apart from anteroposterior dynamics, some genes soon became downregulated at the prospective forebrain floor plate, or allowed to identify an early roof plate domain (dorsoventral pattern). Peculiarities of the telencephalon (initial specification and differentiation of pallium versus subpallium) are contemplated. The basic anterior forebrain subdivisions seem to acquire correlated specification and fate mapping patterns around stage HH8.     

Three intrinsically unstructured mussel adhesive proteins,mfp‐1, mfp‐2, and mfp‐3: Analysis by circular dichroism

Mussel foot proteins (mfps) mediate fouling by the byssal holdfast and have been extensively investigated as models for versatile polymer‐mediated underwater adhesion and coatings. However, insights into the structural properties of mfps have lagged far behind the nanomechanical advances, owing in part to the inability of these proteins to crystallize as well as their limited solubility. Here, solution secondary structures of mfp‐1, mfp‐2, and mfp‐3, localized in the mussel byssal cuticle, adhesive plaque, and plaque–substratum interface, respectively, were investigated using circular dichroism. All three have significant extended coil solution structure, but two, mfp‐1 and mfp‐2, appear to have punctuated regions of structure separated by unstructured domains. Apart from its punctuated distribution, the structure in mfp‐1 resembles other structural proteins such as collagen and plant cell‐wall proteins with prominent polyproline II helical structure. As in collagen, PP II structure of mfp‐1 is incrementally disrupted by increasing the temperature and by raising pH. However, no recognizable change in mfp‐1's PP II structure was evident with the addition with Ca²⁺ and Fe³⁺. In contrast, mfp‐2 exhibits Ca²⁺‐ and disulfide‐stabilized epidermal growth factor‐like domains separated by unstructured sequence. Mfp‐2 showed calcium‐binding ability. Bound calcium in mfp‐2 was not removed by chelation at pH 5.5, but it was released upon reduction of disulfide bonds. Mfp‐3, in contrast, appears to consist largely of unstructured extended coils.