[40], [41]SMPD3 has also been implicated in macrophage differentiation and leukemia. [42] Given SMPD3’s crucial role in development and its expression in neurons in the central nervous system, our observed association with IUS raises intriguing questions about the biological mechanisms underlying smoking’s affect on prenatal growth. Lastly, CRYGN encodes a crystallin, one of the main structural proteins in the eye. [43] Very little research on CRYGN currently exists, thus the implications of our association with IUS with regard to developmental biology are largely unknown. Here, SMPD3 is linked to leukemia.