Figure 1
A three-generation Han Chinese family with AINHL. Hearing loss individuals are indicated by filled symbols. The arrow denotes the proband. Asterisks denote individuals who have a family history of exposure to amino glycosides.
Table 1
Summary of clinical data for several members of this family
| Subjects | I-2 | II-1 | II-5 | III-2 | II-4 |
|---|---|---|---|---|---|
| Gender | female | male | female | male | male |
| Age when tested | 50 | 26 | 30 | 1 | 39 |
| Age at onset | 46 | 18 | 25 | 1 | – |
| Use of aminoglycoside | yes | no | yes | no | no |
| PTA (dB) right ear | 90 | 90 | 100 | 85 | 25 |
| PTA (dB) left ear | 92 | 85 | 100 | 75 | 25 |
| Level of hearing loss | profound | profound | severe | severe | normal |
[i] PTA: pure tone audiometry; dB: decibel.
Figure 2
Air conduction audiogram of family members with the mitochondrial C1494T and G7444A pathogenic variants, subject II-4 was used as a control. Symbols: X: left ear, O: right ear.
Figure 3
Identification G7444A pathogenic variant in the CO1/tRNASer(UCN) gene. Partial sequence chromatograms of COI/tRNASer(UCN) from affected individuals and the healthy control.
Table 2
mtDNA sequence variants in this family with hearing impairment.
| Gene | Position | Replacement | Conservationa | Previously Reportedb |
|---|---|---|---|---|
| D-Loop | 73 | A>G | – | yes |
| 152 | T>C | – | yes | |
| 263 | A>G | – | yes | |
| 16223 | C>T | – | yes | |
| 16519 | T>C | – | yes | |
| 12S rRNA | 827 | A>G | – | yes |
| 1438 | A>G | – | yes | |
| 1494 | C>T | C/C/C/C | yes | |
| 16S rRNA | 2706 | A>G | A/G/A/A | yes |
| 3010 | G>A | G/G/A/A | yes | |
| ND1 | 3497 | C>T (Ala→Val) | – | yes |
| 3970 | C>T | – | yes | |
| ND2 | 4883 | C>T | – | yes |
| CO1 | 7444 | G>A (Term→Lys) | – | yes |
| A6 | 8860 | A>G (Thr→Ala) | – | yes |
| ND3 | 10398 | A>G (Thr→Ala) | – | yes |
| 10400 | C>T | – | yes | |
| ND4 | 11719 | G>A | – | yes |
| ND5 | 12705 | C>T | – | yes |
| Cyt b | 15301 | G>A | – | yes |
| 15426 | A>G (Thr→Ala) | T/M/I/I | yes | |
a Conservation of amino acid for polypeptides or nucleotide for RNAs in human (H), bovine (B), mouse (M), and Xenopus laevis (X).
b See the online mitochondrial genome database (http://www.mitomap.org).
Figure 4
Location of deafness-associted mutations in tRNASer(UCN) and adjacent COI. The arrow indicates the A7445G and G7444A pathogenic variants in the precursor of this tRNA and adjacent sequence of COI from wild-type (WT) and mutant (MT).