Table 3. Summary of mutations detected in the CHM gene in the present study

The molecular weight (MW) of the in vitro translated protein was estimated based on the predicted amino acid (a.a.) sequence with an online program called "Compute pI/Mw tool". Two mutations are novel: c.627dupA and c.703-1G>C. Note that mutations are denoted at the DNA and protein levels by recommended nomenclature [11] and its subsequent online revisions (genomic). The reference sequence used is X78121.1. The "A" nucleotide of the ATG translation initiation codon is numbered as 1 (which used to be designated as nucleotide 31 in most previous reports). IB stands for immunoblot analysis of proteins extracted from leukocytes. The presence of REP-1 is indicated by a plus sign (+) and its absence by a minus sign (-). "nd" stands for "not done", No or no means number. The family with this particular mutation (c.652_655delTCAC) could not be contacted for a second specimen for protein truncation test and immunoblot analysis. But this mutation has been reported previously. For mutation c.703-1G>C, no in vitro translated protein (indicated by "Nil") is produced from CHM-2.2 because the 3' half of the primer NF2 and the whole sequence-specific part of the primer CHM-2FT7myc anneal to exon 6 (Figure 1), which is completely removed from the mRNA and hence cDNA by the splicing mutation.

                                                                          In vitro translated
                                                                          protein. No. of a.a.
                                     In vivo translated protein           (predicted MW, kDa)
                                ---------------------------------------   --------------------
Mutation             Location   Predicted effect     (no. of a.a.)   IB   CHM-1.2    CHM-2.2
------------------   --------   ------------------   -------------   --   --------   ---------
Wildtype                                                (653)        +    496 (56)   428 (49)
c.627dupA            Exon 5     p.Pro210ThrfsX12        (221)        -    231 (26)   428 (49)
c.652_655delTCAC     Exon 5     p.Ser218LysfsX12        (229)        nd   nd         nd
c.703-1G>C           Intron 5   p.Leu235_Gln273del      (614)        -    457 (52)   Nil
c.1019C>A            Exon 8     p.Ser340X               (339)        -    349 (40)   114 (14)
c.1584_1587delTGTT   Exon 13    p.Val529HisfsX6         (534)        -    496 (56)   309 (36)