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Background The symptoms of phosphoribosyl pyrophosphate synthetase 1 (PRPS1) deficiency diseases have been reported to be alleviated by medication. In the present study, we report biochemical data that favor PRPS1 deficiency-related hearing loss as a potential target for pharmaceutical treatment. Methods We recruited 42 probands from subjects aged less than 15 years with a moderate degree of nonsyndromic autosomal-recessive or sporadic sensorineural hearing loss (SNHL) in at least one side. Molecular genetic testing, including targeted exome sequencing (TES) of 129 genes for deafness, and in silico prediction were performed. Results A strong candidate variant (p.A82P) of PRPS1 is co-segregated with SNHL in X-linked recessive inheritance from one Korean multiplex SNHL family. Subsequent measurement of in vitro enzymatic activities of PRPS1 from erythrocytes of affected and unaffected family members, as well as unrelated normal controls, confirmed a pathogenic role of this variant. In detail, compared to normal hearing controls (0.23-0.26 nmol/ml/h), the proband, the affected sibling and their normal hearing mother demonstrated a significantly decreased PRPS1 enzymatic activity (0.07, 0.03 and 0.11 nmol/ml/h, respectively). This novel loss-of-function mutation of PRPS1 (p.A82P) is the ninth and sixth most reported mutation in the world and in Asia, respectively. Conclusions DFNX1 was found to account for approximately 2.4% (1/42) of moderate SNHL in a Korean pediatric population. Confirmation of PRPS1 activity deficiency and an audiologic phenotype that initially begins in a milder form of SNHL, as in our family, should indicate the need for rigorous genetic screening as early as possible.

The present meta-analysis examined the overall average correlation (weighted for sample size and corrected for measurement error) between passage-level second language (L2) reading comprehension and 10 key reading component variables investigated in the research domain. Four high-evidence correlates (with 18 or more accumulated effect sizes: L2 decoding, L2 vocabulary knowledge, L2 grammar knowledge, first language [L1] reading comprehension), and six low-evidence correlates (L2 phonological awareness, L2 orthographic knowledge, L2 morphological knowledge, L2 listening comprehension, working memory, metacognition) were included in the study. For the four high-evidence correlates, a series of moderator analyses were also carried out to examine the effects of age, L2 proficiency, L1–L2 script and language distance, and measurement characteristics. The results showed that L2 grammar knowledge (r = .85), L2 vocabulary knowledge (r = .79), and L2 decoding (r = .56) were the three strongest correlates of L2 reading comprehension. The six low-evidence correlates had moderate-to-strong mean correlations, with L2 listening comprehension being the strongest correlate (r = .77) and metacognition (r = .32) being the weakest correlate. Age, some measurement characteristics, and L1–L2 language distance were found to be significant moderators for some reading components.

This study investigates the contribution of second-language (L2) morphological awareness to foreign language reading comprehension. Tenth graders (n = 188) at a South Korean high school were assessed on 6 reading- and language-related variables: phonological decoding, listening comprehension, vocabulary knowledge, passage-level reading comprehension, metacognitive reading awareness, and morphological awareness. A series of 10 sequential regression analyses were conducted to determine the unique reading variance accounted for by each of the 2 morphological awareness tests included in this study (i.e., the Test of Morphological Structure–Revised [TMS–R], the Verbal Suffix Knowledge Test–Revised [VSKT–R]). The result revealed that morphological awareness was a significant predictor of L2 reading comprehension when other variables were controlled. Of the 2 tests, the TMS–R—a measure that primarily tested derivational morphological knowledge—showed stronger predictability. This provides evidence that morphological awareness, especially derivational morphological knowledge, is an important variable to be considered in explaining L2 reading comprehension among older readers.