It is the interplay between concentrations of Da, AS-C, and Emc proteins that determines whether or not a cell will become an SMC, and later on an SO. In this way, "Emc provides positional information for SO patterning." The levels of each of these proneural proteins is likely to be regulated by the Notch signaling pathway, as the lack of Notch causes an excess of neural cells while "constitutive Notch signaling...suppresses neural differentiation." Notch has been shown to mediate lateral specification of proneural cell-clusters by restricting the expression of AS-C proteins to only the neuroblast, while causing the surrounding dermoblast cells to cease expression of the "as-c" complex. Sex in "Drosophila" is determined in part by the "Sex lethal" ("Sxl") gene; more precisely, it is turned 'on' in females and 'off' in males. Whether or not this gene will be expressed is determined by the ratio of sex chromosomes (X-chromosomes) to autosomal chromosomes. The fly embryo assesses this ratio by the difference between concentrations of the "scute" gene product, which is on the X-chromosome, and the "emc" gene product, which is on an autosomal chromosome. Specifically, Emc proteins inactivate the Sc protein (a transcription factor) and stop transcription of genes on the X-chromosome. As females have twice the amount of Sc as males, they can overcome this obstacle and express the "Sxl" gene. Early support for the role of "emc" came from the mouse "Inhibitor of differentiation" ("Id") gene, which negatively regulates myogenesis by forming a heterodimer with the MyoD protein and therefore inhibiting its abilities as a transcription factor. Similar processes are also likely to exist in other mammals.