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Gene Review

CYP21A1P  -  cytochrome P450, family 21, subfamily A,...

Homo sapiens

Synonyms: CYP21A, CYP21P, P450c21A
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Disease relevance of CYP21A1P


High impact information on CYP21A1P


Chemical compound and disease context of CYP21A1P


Biological context of CYP21A1P

  • Since it is unlikely that the term 'large-scale gene conversion' describes a mechanism that actually occurs between the CYP21A2 and CYP21A1P genes, we propose the discontinuation of that terminology [10].
  • A tandemly duplicated gene designated CYP21A1P (21A), which lies 30 kilobases upstream, contains several point mutations and an 8-base pair deletion so that it cannot encode P450c21 protein; as a result, it is generally considered to be a pseudogene [11].
  • We concluded that the 6.2-kb TaqI fragments of the CYP21A2 haplotype may lead to an incorrect result in the analysis between CYP21A2 and CYP21A1P [12].
  • The 3.7- and 3.2-kb fragments produced by TaqI digestion are respective crucial markers of the CYP21A2 and CYP21A1P genes for the analysis of the RCCX module in chromosome 6p21 [12].
  • During the course of genetic analysis of CYP21A2, we found that misgenotyping of CAH by PCR-based method is possible if both alleles of a CAH patient were deletion mutations and at least one of them carried a CYP21A1P-CYP21A2 fusion gene [13].

Anatomical context of CYP21A1P


Associations of CYP21A1P with chemical compounds

  • Thus, 2 of 15 chromosomes do not carry deletions and may represent gene conversions; 13 of 15 chromosomes studied have a deletion of approximately equal to 30 kb, leaving behind the C4A gene and a single CYP21A-like gene [16].
  • However, the large size (approximately 30 kb) of the individual CYP21 + C4 repeat units together with the difficulty in identifying reliable CYP21A- and CYP21B-specific markers has prevented direct monitoring of gene organization on individual haplotypes by conventional Southern analyses [17].
  • CONCLUSION: These data suggest that these CpG dinucleotides are more frequently mutated in CYP21 than in CYP21P, and that several mutations at CpG dinucleotides in the coding regions of CYP21 might result from CpG instability rather than the more usually proposed mechanism of gene conversion [9].
  • RESULTS: Intron 2 of CYP21P contains frequent SNPs around nucleotide 398 and nucleotide 509, which can be typed by PCR/restriction enzyme digestion with HaeIII [9].

Physical interactions of CYP21A1P

  • All eight chimeric CYP21 genes coupled with HLA-Bw47 in five unrelated patients had the CYP21A-CYP21B sequence transition within the same gene region (+1375 to +1993) [18].

Regulatory relationships of CYP21A1P


Other interactions of CYP21A1P

  • Hybridization with specific oligonucleotide probes showed that in all 13 cases this remaining CYP21 gene carried an 8-base-pair deletion, typical of CYP21A, that prevents synthesis of a functional protein [16].
  • Sequences promoting the transcription of the human XA gene overlapping P450c21A correctly predict the presence of a novel, adrenal-specific, truncated form of tenascin-X [20].
  • In the present experiments we cultured primary human adrenocortical cells in defined medium and used RNase protection assays to examine whether there might be a selective increase in the relative abundance of CYP21P transcripts under any of the various regulatory factors known to affect expression of 21-hydroxylase [21].
  • All patients with the G424S mutation presented CYP21P and C4A gene deletions and human leukocyte antigen DR17 on the same haplotype, suggesting a linkage disequilibrium and a probable founder effect [22].

Analytical, diagnostic and therapeutic context of CYP21A1P

  • Sequence analysis revealed that this allele carried two missense mutations, R339H and P453S, neither of which has been previously observed in CYP21A or CYP21B [23].
  • It has been demonstrated that one reaction for PCR amplification of the CYP21 gene and the chimeric CYP21P/CYP21 gene using mixed primers in combination with nested PCR and single-strand conformation polymorphism is considered highly efficient and accurate for molecular diagnosis of CAH due to 21-hydroxylase deficiency [24].
  • The molecular diagnosis of CAH, important for prenatal diagnosis, carrier detection, and a better understanding of the various clinical CAH forms, is complicated by the close proximity of a highly similar pseudogene, CYP21A, containing (and probably donating, by gene conversion-like events) most of the defects underlying CAH [25].
  • Densitometry of the autoradiographs was used to determine the ratio of the copy-number of the 21-hydroxylase gene (CYP21B) to the copy-number of its pseudogene (CYP21A) [26].
  • However, the diagnosis of classic 21-hydroxylase deficiency was obtained by Southern blotting studies, showing that she was homozygous for the 30-kb deletion, including the 3' end of CYP21P pseudogene, the C4B gene, and the 5' end of the functional CYP21 gene [27].


  1. Phenotype and genotype correlation of the microconversion from the CYP21A1P to the CYP21A2 gene in congenital adrenal hyperplasia. Torres, N., Mello, M.P., Germano, C.M., Elias, L.L., Moreira, A.C., Castro, M. Braz. J. Med. Biol. Res. (2003) [Pubmed]
  2. Preliminary investigation of mutations in 21-hydroxylase gene in patients with congenital adrenal hyperplasia in Russia. Evgrafov, O.V., Polyakov, A.V., Dzenis, I.G., Baharev, V.A. Hum. Mutat. (1995) [Pubmed]
  3. A mutation (Pro-30 to Leu) in CYP21 represents a potential nonclassic steroid 21-hydroxylase deficiency allele. Tusie-Luna, M.T., Speiser, P.W., Dumic, M., New, M.I., White, P.C. Mol. Endocrinol. (1991) [Pubmed]
  4. Organ-specific and non-organ-specific autoantibodies in children and young adults with autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED). Perniola, R., Falorni, A., Clemente, M.G., Forini, F., Accogli, E., Lobreglio, G. Eur. J. Endocrinol. (2000) [Pubmed]
  5. A de novo pathological point mutation at the 21-hydroxylase locus: implications for gene conversion in the human genome. Collier, S., Tassabehji, M., Sinnott, P., Strachan, T. Nat. Genet. (1993) [Pubmed]
  6. Congenital adrenal hyperplasia due to 21-hydroxylase deficiency. White, P.C., Speiser, P.W. Endocr. Rev. (2000) [Pubmed]
  7. Deficiencies of human complement component C4A and C4B and heterozygosity in length variants of RP-C4-CYP21-TNX (RCCX) modules in caucasians. The load of RCCX genetic diversity on major histocompatibility complex-associated disease. Blanchong, C.A., Zhou, B., Rupert, K.L., Chung, E.K., Jones, K.N., Sotos, J.F., Zipf, W.B., Rennebohm, R.M., Yung Yu, C. J. Exp. Med. (2000) [Pubmed]
  8. Gene conversions and unequal crossovers between CYP21 (steroid 21-hydroxylase gene) and CYP21P involve different mechanisms. Tusié-Luna, M.T., White, P.C. Proc. Natl. Acad. Sci. U.S.A. (1995) [Pubmed]
  9. Single-nucleotide polymorphisms in intron 2 of CYP21P: evidence for a higher rate of mutation at CpG dinucleotides in the functional steroid 21-hydroxylase gene and application to segregation analysis in congenital adrenal hyperplasia. Jiddou, R.R., Wei, W.L., Sane, K.S., Killeen, A.A. Clin. Chem. (1999) [Pubmed]
  10. Carriership of a defective tenascin-X gene in steroid 21-hydroxylase deficiency patients: TNXB -TNXA hybrids in apparent large-scale gene conversions. Koppens, P.F., Hoogenboezem, T., Degenhart, H.J. Hum. Mol. Genet. (2002) [Pubmed]
  11. Abundant adrenal-specific transcription of the human P450c21A "pseudogene". Bristow, J., Gitelman, S.E., Tee, M.K., Staels, B., Miller, W.L. J. Biol. Chem. (1993) [Pubmed]
  12. Diversity of the CYP21A2 gene: a 6.2-kb TaqI fragment and a 3.2-kb TaqI fragment mistaken as CYP21A1P. Lee, H.H., Tsai, F.J., Lee, Y.J., Yang, Y.C. Mol. Genet. Metab. (2006) [Pubmed]
  13. Pitfalls of PCR-based genotyping in patients with 21-hydroxylase deficiency. Tsai, C.H., Lin, W.D., Tsai, F.J., Peng, C.T., Wu, J.Y. Acta paediatrica Taiwanica = Taiwan er ke yi xue hui za zhi. (2001) [Pubmed]
  14. The suppression effect of DNA sequences within the C4A region on the transcription activity of human CYP21. Chang, S.F., Cheng, C.L. Endocr. Res. (1998) [Pubmed]
  15. A novel semiquantitative polymerase chain reaction/enzyme digestion-based method for detection of large scale deletions/conversions of the CYP21 gene and mutation screening in Turkish families with 21-hydroxylase deficiency. Tukel, T., Uyguner, O., Wei, J.Q., Yuksel-Apak, M., Saka, N., Song, D.X., Kayserili, H., Bas, F., Gunoz, H., Wilson, R.C., New, M.I., Wollnik, B. J. Clin. Endocrinol. Metab. (2003) [Pubmed]
  16. Characterization of frequent deletions causing steroid 21-hydroxylase deficiency. White, P.C., Vitek, A., Dupont, B., New, M.I. Proc. Natl. Acad. Sci. U.S.A. (1988) [Pubmed]
  17. Pulsed field gel electrophoresis identifies a high degree of variability in the number of tandem 21-hydroxylase and complement C4 gene repeats in 21-hydroxylase deficiency haplotypes. Collier, S., Sinnott, P.J., Dyer, P.A., Price, D.A., Harris, R., Strachan, T. EMBO J. (1989) [Pubmed]
  18. Two distinct areas of unequal crossingover within the steroid 21-hydroxylase genes produce absence of CYP21B. Donohoue, P.A., Jospe, N., Migeon, C.J., Van Dop, C. Genomics (1989) [Pubmed]
  19. A novel frameshift mutation (141delT) in exon 1 of the 21-hydroxylase gene (CYP21) in a patient with the salt wasting form of congenital adrenal hyperplasia. Mutation in brief no. 255. Online. Krone, N., Braun, A., Roscher, A.A., Schwarz, H.P. Hum. Mutat. (1999) [Pubmed]
  20. Sequences promoting the transcription of the human XA gene overlapping P450c21A correctly predict the presence of a novel, adrenal-specific, truncated form of tenascin-X. Tee, M.K., Thomson, A.A., Bristow, J., Miller, W.L. Genomics (1995) [Pubmed]
  21. CYP21 pseudogene transcripts are much less abundant than those from the active gene in normal human adrenocortical cells under various conditions in culture. Endoh, A., Yang, L., Hornsby, P.J. Mol. Cell. Endocrinol. (1998) [Pubmed]
  22. A novel missense mutation, GLY424SER, in Brazilian patients with 21-hydroxylase deficiency. Billerbeck, A.E., Bachega, T.A., Frazatto, E.T., Nishi, M.Y., Goldberg, A.C., Marin, M.L., Madureira, G., Monte, O., Arnhold, I.J., Mendonca, B.B. J. Clin. Endocrinol. Metab. (1999) [Pubmed]
  23. R339H and P453S: CYP21 mutations associated with nonclassic steroid 21-hydroxylase deficiency that are not apparent gene conversions. Helmberg, A., Tusie-Luna, M.T., Tabarelli, M., Kofler, R., White, P.C. Mol. Endocrinol. (1992) [Pubmed]
  24. CYP21 mutations and congenital adrenal hyperplasia. Lee, H. Clin. Genet. (2001) [Pubmed]
  25. Identification of molecular defects causing congenital adrenal hyperplasia by cloning and differential hybridization of polymerase chain reaction-amplified 21-hydroxylase (CYP21) genes. Helmberg, A., Tabarelli, M., Fuchs, M.A., Keller, E., Dobler, G., Schnegg, I., Knorr, D., Albert, E., Kofler, R. DNA Cell Biol. (1992) [Pubmed]
  26. Molecular analysis of CYP21 and C4 genes in Brazilian families with the classical form of steroid 21-hydroxylase deficiency. de-Araujo, M., Sanches, M.R., Suzuki, L.A., Guerra, G., Farah, S.B., de-Mello, M.P. Braz. J. Med. Biol. Res. (1996) [Pubmed]
  27. How a patient homozygous for a 30-kb deletion of the C4-CYP 21 genomic region can have a nonclassic form of 21-hydroxylase deficiency. L'Allemand, D., Tardy, V., Grüters, A., Schnabel, D., Krude, H., Morel, Y. J. Clin. Endocrinol. Metab. (2000) [Pubmed]
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