TBX1 and 22q11.2 deletion syndrome: Clinical conditions known to impact these stromal cell populations are chromosome 22q11.2 deletion syndrome (22q11.2del), also referred to as DiGeorge syndrome, Coloboma-heart defects-atresia choanae-retardation of growth-genital abnormalities-ear (CHARGE) syndrome arising from mutations in Chromodomain Helicase DNA Binding Protein 7 (CHD7), Nude/SCID due to autosomal recessive mutations in Forkhead Box N1 (FOXN1), otofaciocervical syndrome type 2 (OTFCS2) due to mutations in PAX1, as well as mutations in TBX1 (located within the chromosome 22q11.2 locus) and TBX2 (Table 1) (9–17).