The main purpose of the Human Cytochrome P450 (CYP) Allele Nomenclature
website is the management of an official and unified allele designation
system, as well as the provision of a database of CYP alleles and their associated
The nomenclature system adheres to the guidelines provided in Shows
et al (1987), Daly
et al (1996), Antonarakis and the Nomenclature Working Group (1998)
Dunnen and Antonarakis
- On this website only
human CYP and POR alleles are considered.
gene and the allele name is separated by an asterisk followed by Arabic
numerals designating the specific allele (e.g. CYP1A1*3).
- For allele
designation, sequence information of at least all exons and exon-intron
borders must be submitted.
be assigned a unique allele name, the sequence should contain at least
one nucleotide change that has been shown to affect transcription,
splicing, translation, posttranscriptional or posttranslational
modifications or result in at least one amino acid change. So-called
sub-alleles containing additional non-functional variations in addition
to the functional ones described (e.g. CYP2D6*10B) will no longer be designated.
a new sequence variation causing functional consequences is shown to exist in
different combinations with other sequence variations not causing functional
effects, the sequence with the lowest number of additional variations will be
chosen for allele designation.
- If a sequence
variation causing detrimental effects (e.g. the 1846G>A variation in CYP2D6*4 causing a splicing
defect) is shown to exist together with other variations causing
functional effects, the variation causing the detrimental effect will
determine the name of the allele (e.g. CYP2D6*4B).
- If sequence
variations causing functional effects of similar magnitude (e.g. amino
acid substitutions) are found to exist together as well as on their own,
the combination allele will be given a new allele name (see e.g. CYP2D6*102 and *103).
- For extra gene
copies (n) placed in tandem on the same chromosome the entire allelic
arrangement should be referred to as e.g. CYP2D6*2Xn.
- Nucleotides are
numbered according to the base A in the initiation codon ATG as +1 and
the base before A as -1.
- The names for the
corresponding proteins have a period between the name of the gene
product and the allele number (e.g. CYP2D6.2). If the allele is unable
to produce full length protein, no protein name will be assigned.
that are not easily assigned to a specific allele are listed at the
bottom of the corresponding gene webpage in a separate SNP table.
sequence variations causing functional consequences that have an unclear
linkage with other variations causing functional effects will not be
- All submissions are
kept confidential and new allele names are on request kept confidential
until publication. Authors are encouraged to submit their novel allele
to the CYP-allele website prior to submission to a journal, especially
since many Editors request naming of new alleles by the CYP-allele
website prior to publication. Journal publication is however not a
requirement for publication on the CYP-allele website.
14. Usage of
star (*) allele designations resembling those officially designated by the
CYP-allele Nomenclature committee is highly discouraged due to the apparent
risk of confusion.
information on in vitro or in vivo activity analyses for known
CYP alleles can at any time be submitted to the
CYP-allele website for inclusion with the respective allele.
- All variants identified through Next Generation
Sequencing (NGS) techniques must be confirmed through Sanger sequencing
or another independent method. Furthermore, NGS sequence data must at a
minimum have 100% coverage over exons and exon-flanking regions to be
considered for allele name assignments.