Subtle mutations in the SMN1 gene in Chinese patients with SMA: p.Arg288Met mutation causing SMN1 transcript exclusion of exon7

Table 1 Genotype and phenotype in patients with a subtle mutation of SMN1 gene

Family No.	Case No.	PhenoType	Gender	Age at last examination	Age of onset	Attained motor function			SMN1 genotype		Point Mutationlocation	SMN2 copies	Fl-SMN2 transcript	Fl-SMN transcript	Parental origin
						Head control	Sit unsupported	Walk independently	Allele1	Allele2
1	1	I	M	3y6m	4 m	+	-	-	Deletion	p.Ser8LysfsX23	Exon 1	2	-	-	ND
2	2	II	M	1y7m	11 m	+	+	-	Deletion	p.Ser8LysfsX23	Exon 1	2	6.33 ± 1.72	6.76 ± 1.94	Paternal
3	3	II	M	6y8m	1y2m	+	+	-	Conversion	p.Ser8LysfsX23	Exon 1	3	20.36 ± 11.09	21.01 ± 10.4	Paternal
4	4	II	M	5y	11 m	+	+	-	Deletion	p.Glu134Lys	Exon 3	2	7.73 ± 5.44	12.46 ± 5.47	Paternal
5	5	II	F	2y6m	1y1m	+	+	-	Deletion	p.Glu134Lys	Exon 3	2	6.41 ± 5.78	11.21 ± 3.45	Paternal
6	6	I	F	2y3m	4 m	+	-	-	Deletion	p.Leu228X	Exon 5	2	9.24 ± 6.6	10.277 ± 6.8	Maternal
7	7	II	M	4y1m	8 m	+	+	-	Conversion	p.Leu228X	Exon 5	3	-	-	ND
8	8	II	M	14y	10 m	+	+	-	Deletion	p.Ser230Leu	Exon 5	2	8.04 ± 7.27	12.22 ± 7.07	Paternal
8	9	III	F	9y8m	2y	+	+	+†	Deletion	p.Ser230Leu	Exon 5	2	9.35 ± 5.74	14.83 ± 4.45	Paternal
9	10	II	M	6y4m	1y	+	+	-	Deletion	p.Tyr277Cys§	Exon 6	2	4.53 ± 3.47	6.54 ± 4.33	Maternal
10	11#	I	F	2y10m	5 m	+	-	-	Conversion	p.Arg288Met	Exon 7	3	13.1 ± 10.4	13.71 ± 10.6	Paternal
11	12#	II	F	4y4m	1y6m	+	+	-	Conversion	p.Arg288Met	Exon 7	3	9.46 ± 7.84	12.46 ± 8.01	Paternal
12	13	II	M	5y	10 m	+	+	-	Deletion	-	-	2	8.02 ± 1.97	9.86 ± 2.01	ND
13	14	III	M	15y	1y5m	+	+	+†	Conversion	-	-	3	21.67 ± 11.0	25.17 ± 11.8	ND

Conversion means deletion of SMN1 owing to conversion of SMN1 sequences to SMN2 with the copy number of SMN2 increasing. ND, not detected. §Novel mutation; #,these patients had been reported [22]; †, Walk in waddling gait ;case 8 and case 9 are siblings.

ISSN: 1471-2350