A transmitted deletion of 2q13 to 2q14.1 causes no phenotypic abnormalities

E ditor -An imbalance of genetic material, especially monosomy, will usually give rise to an abnormal phenotype. A few instances of proximal 2q deletions have been published, but previous cases (q12-q14, 1 q12-q14.2, 2 q14-q21 3 4 ) have been associated with clinical features such as mental retardation, facial dysmorphism, heart defects, and renal and digital anomalies. 3 We ascertained an interstitial deletion of chromosome 2 at q13-q14.1 (fig 1 ) in a clinically normal G6, P2, SAB3 woman aged 38. She had been referred for chromosome analysis following three successive miscarriages at 8½, before 11, and at 7 weeks' gestation. Her current pregnancy was chromosomally normal at amniocentesis and continuing at 26 weeks. Testing of her two previous children was not being pursued at the time of writing. This deletion was subsequently found to have been transmitted by her G2, P2 mother who had no associated phenotype nor history of miscarriages. Cytogenetic analysis at the 600 band level failed to detect a subtle insertional translocation of the missing material elsewhere in the genome and the partners of both mother and daughter had normal karyotypes. Here we have attempted to define the extent of this deletion and thereby the degree of euchromatic loss using fluorescence in situ hybridisation (FISH).

Whole chromosome 2 paint (Cambio) corroborated our cytogenetic results in that no fluorescent signal was detected outside the two chromosomes 2 to account for the missing bands at 2q13-q14.1. To exclude an intrachromosomal insertion and to help identify the loci most proximal and distal to the deletion, a range of eight YACs (YAC Screening Centre, Milan) spanning proximal 2q were applied (table 1 ). At least five metaphases in either the proband or her mother were scored for a positive signal at each of these loci along with control probes at either the centromere (D2Z1) or distal to the deletion at 2q21 (845f5).

YAC name 1-150	Database location 1-150	Laboratory location 1-151	STS No 1-150	Distance from short arm telomere (cM) 1-150	FISH result
636b10	q12-q13	q12-q13	D2S135	120	Normal
791f4	q13	q13	D2S1895	128	Partially deleted
817b4	q14	q14.1	D2S308	129	Deleted
786a12	q14	q14.1	D2S363	130	Deleted
679d2	q12-q14	q14.3	D2S110	135	Normal
821h9	q14	q14.3	D2S347	136	Normal
845f5	q12	q21	D2S1888	126