Transcriptional Activation and Repression Every gene is controlled uniquely, whether in its spatial or temporal pattern of expression or in its response to extracellular signals. It is estimated that transcription factors account for ~30% of expressed genes. A growing number of identified genetic diseases involve transcription factors (Table 62-2). The MODY (maturity-onset diabetes of the young) disorders are representative of this group of diseases; mutations in several different islet cell–specific transcription factors cause various forms of MODY (Chap. 338). Table 62-2 Selected Examples of Diseases Caused by Mutations and Rearrangements in Transcription Factor Classes Transcription Factor Class Example Associated Disorder Nuclear receptors Androgen receptor Complete or partial. | Chapter 062. Principles of Human Genetics Part 7 Transcriptional Activation and Repression Every gene is controlled uniquely whether in its spatial or temporal pattern of expression or in its response to extracellular signals. It is estimated that transcription factors account for 30 of expressed genes. A growing number of identified genetic diseases involve transcription factors Table 62-2 . The MODY maturity-onset diabetes of the young disorders are representative of this group of diseases mutations in several different islet cell-specific transcription factors cause various forms of MODY Chap. 338 . Table 62-2 Selected Examples of Diseases Caused by Mutations and Rearrangements in Transcription Factor Classes Transcription Factor Class Example Associated Disorder Nuclear receptors Androgen receptor Complete or partial androgen insensitivity recessive missense mutations Spinobulbar muscular atrophy CAG repeat expansion Zinc finger proteins WT1 WAGR syndrome Wilm s tumor aniridia genitourinary malformations mental retardation Basic helix-loop-helix MITF Waardenburg syndrome type 2A Homeobox IPF1 Maturity onset of diabetes mellitus type 4 heterozygous mutation haploinsufficiency Pancreatic agenesis homozygous mutation Leucine zipper Retina leucine zipper NRL Autosomal dominant retinitis pigmentosa High mobility group HMG proteins SRY Sex-reversal Forkhead HNF4a HNFla HNFlp Maturity-onset of diabetes mellitus types 1 3 5 Paired box PAX3 Waardenburg syndrome types 1 and 3 T-box TBX5 Holt-Oram syndrome thumb anomalies atrial or ventricular septum defects phocomelia
