Complex sentence: It is related to the alternative splicing factors Rbfox1 and Rbfox2, but instead of its involvement in splicing, it is most well-known as the nuclear biomarker NeuN.
Split into simpler sentences: It is related to the alternative splicing factors Rbfox1 and Rbfox2, but it not known to be involved in splicing. Instead, it is most well-known as the nuclear biomarker NeuN.