2. The first character of a gene symbol must be a letter - preferably the initial letters in the gene symbol and the corresponding gene name should be the same.
3. In text, the gene symbols should normally be given in italics, beginning with a capital letter. Remaining letters should be written in lower case. An author may decide to waive the requirement of using italics if he so wishes.
4. If a human gene symbol exists, the same symbol should be used in the rat (except for the lower case letters). Thus, the list of human gene symbols could be looked upon as a reserved symbols list for rat genes. Similarly, if a particular gene already has been given a symbol in the mouse, the corresponding rat gene should be given the same symbol. The rat gene nomenclature subcommittee will be in contact with the human and mouse nomenclature committees, in order to continually adjust the rat symbols to conform with symbols in other mammalian species.
5. Symbols for related genes, such as genes belonging to the same gene family, will usually have the same common stem of 2-4 characters, followed by 1-2 distinguishing characters. Some characters at the end of gene symbols have special meanings, e.g. r usually means receptor, bp means binding protein, rs means related sequence etc.
6. Naturally, a proposed new symbol must not duplicate one already in use for another locus. When choosing a new symbol, check it for uniqueness in the RATMAP database, in the human genome database (GDB), and in the mouse genome database (MGD). If you are uncertain about a gene symbol, contact one of the members of the subcommittee.
7. When a well-known locus has been recognized initially by a mutation and later the structural gene is identified, the locus can be identified by either symbol, e.g. B (brown locus)=Tyrp (tyrosine phosphatase), C (albino locus)=Tyr (tyrosinase).
8. Special rules apply to loci identified by certain DNA segments. These loci should be given unique D-symbols (D for DNA) and they are used in two ways: Firstly, loci identified by anonymous DNA probes should be given D-symbols. Secondly, intragenic loci may be given D-symbols. A gene is a functional unit that may span several kb of DNA. Thus, assays such as PCR may detect intragenic variation in the DNA (e.g microsatellites) and D-symbols may be used to specify the site in which the intragenic variation occurs. Normally, the corresponding gene symbol should be used in text even when a probe exhibiting intragenic variation has been used. The D-symbol is only used when describing intragenic mapping analysis, or when stating that the gene was typed using an intragenic D-locus.
9. D-symbols are composed of four parts: (i) D for DNA; (ii) 1--20, X and Y for the rat chromosomal assignment (0 for an unmapped locus); (iii) a 1-3 letter laboratory code, indicating the laboratory or the scientist describing the locus. Only the first letter of the laboratory code is capitalized. Laboratory codes are assigned from a central registry and can be obtained by contacting the Institute of Laboratory Animal Resources (ILAR) in Washington, D.C., USA. The present contact person is Dr. Dorothy Greenhouse (fax: +1 - 202 334 1687); (iv) a unique serial number. It is preferred that numbers be assigned to loci in the order the loci are described on each chromosome for a particular laboratory, e.g. D1Pas5 would be the fifth D-locus developed and mapped to chromosome 1 at the Pasteur Institute. The use of a number from the probe that detects the locus, e.g. D5Got48 to describe a chromosome 5 locus detected by probe pGL48 of the Gothenburg laboratory, is discouraged.
10. For an anonymous DNA sequence that has been previously mapped in another species, but cross-hybridizes to a corresponding sequence in the rat, the rat symbol is is constructed in the following way: (i) D for DNA; (ii) 1--20, X and Y for the rat chromosomal assignment (0 for an unmapped locus); (iii) the D-symbol of the original locus with the change of the first letter (the D) into H (for a human gene) or M (for a mouse gene). Thus if the human sequence D15S12 is mapped to chromosome 12 in the rat, the locus should be designated D12H15S12. Similarly, if a mouse sequence D4Rp1 (mapping to chromosome 4 in the mouse) is mapped to chromosome 5 in the rat, the locus will be designated D5M4Rp1.