Novel m.4268T>C mutation in the mitochondrial tRNAIle gene is associated with hearing loss in two Chinese families

Table 1 Summary of mitochondrial DNA variants in two Chinese families with deafness

Gene	Position	Replacement	AA Position	Conservation (H/B/M/X)a	CRS	A23	A27	Previously reportedb
D-loop	73	A to G			A	G	G	Yes
	195	T to C			C	C	C	Yes
	249	Del A			A	Del A	Del A	Yes
	263	A to G			A	G	G	Yes
	309	C to CC			C	CC	CC	Yes
	310	T to CTC			T	CTC	CTC	Yes
	16304	T to C			T	C	C	Yes
12S rRNA	750	A to G		A/A/A/-	A	G	G	Yes
	1005	T to C		T/T/T/T	T		C	Yes
	1438	A to G		A/A/A/G	A	G	G	Yes
	1824	T to C		T/A/A/A	T	C	C	Yes
16S rRNA	2706	A to G		A/G/A/A	A	G	G	Yes
ND1	3970	C to T			C	T	T	Yes
	4084	G to A	Val260Ile	V/M/T/M	G	A	A	Yes
	4216	G to A			G	A		Yes
tRNAIle	4268	T to C		T/T/T/T	T	C	C	No
ND2	4769	A to G			A	G	G	Yes
	6392	T to C			T	C	C	Yes
CO1	7028	C to T			C	T	T	Yes
	7828	A to G			A	G	G	Yes
A6	8860	A to G	Thr112Ala	T/A/A/T	A	G	G	Yes
CO3	9612	G to C	Val136Leu	V/V/V/V	G	C	C	Yes
ND3	10310	G to A			G	A	A	Yes
ND4L	10535	T to C			T	C	C	Yes
	10586	G to A			G	A	A	Yes
ND4	11696	G to A	Val313Ile	V/T/T/M	G	A	A	Yes
	11719	G to A			G	A	A	Yes
ND5	13708	G to A	Ala458Thr	S/T/S/T	G	A	A	Yes
	13928	G to C	Ser531Thr	L/S/N/T	G	C	C	Yes
	14002	A to G	Thr556Ala	T/I/I/S	A	G	G	Yes
ND6	14560	G to A			G	A		Yes
Cytb	14766	C to T	Thr7Ile	T/S/T/S	C	T	T	Yes
	15326	A to G	Thr194Ala	T/M/I/I	A	G	G	Yes
	15862	T to C			T		C	Yes

^aConservation of amino acid for polypeptides or nucleotide for RNAs in human (H), bovine (B), mouse (M), and Xenopus laevis (X).

^bSee online mitochondrial genome databases: http://www.mitomap.org and http://www.genpat.uu.se/mtDB. CRS: Cambridge reference sequence.