Highlights d Heterozygous missense mutations in SMARCA2 impair neural differentiation d SMARCA2 mutations result in enhancer reprogramming due to SMARCA4 retargeting d SOX3-dependent neural enhancers are lost in SMARCA2 mutant neural progenitor cells d AP-1 factors drive de novo enhancer formation in SMARCA2 mutant cells

A quasi-distributed pH sensing system was developed to utilize information derived from evanescently excited fluorescence signals originating from sensor sites fabricated on an optical fibre. The sensor sites comprise a section of fibre core exposed by polishing upon which is laid down a sensing film. The film comprises a fluorescent indicator dye immobilized covalently within a hydrogel matrix which is then photopolymerized and attached covalently to the exposed fibre core. Position information is determined from the propagation delay of the returning signals. A system comprising eight sensors spaced at 10 m intervals along an optical fibre has been constructed and characterized. The sensors operate in the region pH 6-pH 8 with a response time of 500 s. The properties of the immobilized indicator dye are found to be similar to those of the dye in aqueous solution. Furthermore, the sensing films so created are found to be resistant to dye leaching.

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ABSRACT A Quasi-distributed pH sensing system based on Optical Time Domain Reflectometry (OTDR) was developed to determine the spatial and intensity information from fluorescence signals coupled back into a single fibre. The evanescent wave due to a 488nm light pulse from a N2 pumped dye laser was used to excite a pH sensitive fluorophore and the emission around 5 1 5nm was detected. A 3dB Y-coupler was used to convey excitation light to the sensing sites and to deliver emission signals from these sites back to a filtered photomultiplier tube. Data collection was performed using a HP 54540A 500MHz digital scope and analysis was carried out using a dedicated Pentium 166MHz PC.A reproducible laboratory fabrication process was developed to produce sensing sites at discrete intervals along the length of the fibre. A polishing process carefully removed the cladding at each sensing site and photo-polymerisation was then used to covalently bind the fluorophore fluorescein with a co-polymer directly onto the site. The results show the sensors performance over a range ofpH4-pHlO with a pKa value of 6.3.The present system was chosen to have sites lOm apart, however, based on the propagation rate of 5ns m1 for light in the fibre and iOns for the fluorescence lifetime, a resolution ofapproximately im is possible.