CLRN1 Is Nonessential in the Mouse Retina but Is Required for Cochlear Hair Cell Development

Mutations in the CLRN1 gene cause Usher syndrome type 3 (USH3), a human disease characterized by progressive blindness and deafness. Clarin 1, the protein product of CLRN1, is a four-transmembrane protein predicted to be associated with ribbon synapses of photoreceptors and cochlear hair cells, and recently demonstrated to be associated with the cytoskeleton. To study Clrn1, we created a Clrn1 knockout (KO) mouse and characterized the histological and functional consequences of Clrn1 deletion in the retina and cochlea. Clrn1 KO mice do not develop a retinal degeneration phenotype, but exhibit progressive loss of sensory hair cells in the cochlea and deterioration of the organ of Corti by 4 months. Hair cell stereocilia in KO animals were longer and disorganized by 4 months, and some Clrn1 KO mice exhibited circling behavior by 5–6 months of age. Clrn1 mRNA expression was localized in the retina using in situ hybridization (ISH), laser capture microdissection (LCM), and RT–PCR. Retinal Clrn1 transcripts were found throughout development and adulthood by RT–PCR, although expression peaked at P7 and declined to undetectable levels in adult retina by ISH. LCM localized Clrn1 transcripts to the retinas inner nuclear layer, and WT levels of retinal Clrn1 expression were observed in photoreceptor-less retinas. Examination of Clrn1 KO mice suggests that CLRN1 is unnecessary in the murine retina but essential for normal cochlear development and function. This may reflect a redundancy in the mouse retina not present in human retina. In contrast to mouse KO models of USH1 and USH2, our data indicate that Clrn1 expression in the retina is restricted to the Müller glia. This is a novel finding, as most retinal degeneration associated proteins are expressed in photoreceptors, not in glia. If CLRN1 expression in humans is comparable to the expression pattern observed in mice, this is the first report of an inner retinal protein that, when mutated, causes retinal degeneration

Distal biceps reconstruction using an Achilles tendon allograft, transosseous EndoButton, and Pulvertaft weave with tendon wrap technique for retracted, irreparable distal biceps ruptures

Background: Distal biceps ruptures can result in ongoing pain and weakness when treated nonoperatively. If retraction of the tendon renders primary repair impossible, reconstruction using a graft is recommended. The current literature includes a variety of techniques with studies reporting small patient numbers. The aim of this study was to report the results of a larger cohort of patients using a technique modified from those previously described in the literature. Methods: Twenty-one consecutive male patients underwent distal biceps reconstruction through 2 small anterior incisions using an Achilles tendon allograft that was fixed distally using a transosseous EndoButton and secured proximally using a Pulvertaft weave and tendon wrap. The mean age was 44 years, and the mean time to surgery was 25 months (range, 2-96 months). Functional outcomes were collected prospectively. Results: The mean preoperative Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) score (11 patients) was 1.9 (range, 0-4.5). The mean postoperative Oxford Elbow Score, QuickDASH score, and Mayo Elbow Performance Score were 44.7 (range, 35-48), 4 (range, 0-20.5), and 92.9 (range, 70-100), respectively, at a mean follow up of 15 months (range, 6-35 months). The mean postoperative QuickDASH score was significantly improved compared with preoperatively (P &lt; .001). All patients were satisfied and all returned to their previous level of activity. There were 2 transient lateral antebrachial cutaneous nerve paresthesias, and 2 patients had a 5° extension lag. There were no other complications. Conclusion: Achilles allograft reconstruction of retracted irreparable distal biceps ruptures provides consistently good results with few complications using this technique. Level of evidence: Level IV; Case Series; Treatment Study.</p

CLRN1 is nonessential in the mouse retina but is required for cochlear hair cell development.

Mutations in the CLRN1 gene cause Usher syndrome type 3 (USH3), a human disease characterized by progressive blindness and deafness. Clarin 1, the protein product of CLRN1, is a four-transmembrane protein predicted to be associated with ribbon synapses of photoreceptors and cochlear hair cells, and recently demonstrated to be associated with the cytoskeleton. To study Clrn1, we created a Clrn1 knockout (KO) mouse and characterized the histological and functional consequences of Clrn1 deletion in the retina and cochlea. Clrn1 KO mice do not develop a retinal degeneration phenotype, but exhibit progressive loss of sensory hair cells in the cochlea and deterioration of the organ of Corti by 4 months. Hair cell stereocilia in KO animals were longer and disorganized by 4 months, and some Clrn1 KO mice exhibited circling behavior by 5-6 months of age. Clrn1 mRNA expression was localized in the retina using in situ hybridization (ISH), laser capture microdissection (LCM), and RT-PCR. Retinal Clrn1 transcripts were found throughout development and adulthood by RT-PCR, although expression peaked at P7 and declined to undetectable levels in adult retina by ISH. LCM localized Clrn1 transcripts to the retinas inner nuclear layer, and WT levels of retinal Clrn1 expression were observed in photoreceptor-less retinas. Examination of Clrn1 KO mice suggests that CLRN1 is unnecessary in the murine retina but essential for normal cochlear development and function. This may reflect a redundancy in the mouse retina not present in human retina. In contrast to mouse KO models of USH1 and USH2, our data indicate that Clrn1 expression in the retina is restricted to the Müller glia. This is a novel finding, as most retinal degeneration associated proteins are expressed in photoreceptors, not in glia. If CLRN1 expression in humans is comparable to the expression pattern observed in mice, this is the first report of an inner retinal protein that, when mutated, causes retinal degeneration

Mapping the malaria parasite drug-able genome using in vitro evolution and chemogenomics

Chemogenetic characterization through in vitro evolution combined with whole-genome analysis can identify novel antimalarial drug targets and drug resistance genes. We performed a genome analysis of 262 Plasmodium falciparum parasites resistant to 37 diverse compounds. This study reveals 159 gene amplifications and 148 nonsynonymous changes in 83 genes associated with resistance acquisition where gene amplifications contribute to 1/3 of drug resistance acquisition events. Beyond confirming previously identified multidrug resistance mechanisms we find new drug target-inhibitor pairs, including: thymidylate synthase and a benzoquinazolinone, farnesyltransferase and a pyrimidinedione, and a dipeptidylpeptidase and an arylurea. This exploration of the P. falciparum resistome and drug-able genome will likely guide drug discovery and structural biology efforts, while also advancing our understanding of resistance mechanisms available to the malaria parasite

Mapping the malaria parasite drug-able genome using<i>in vitro</i>evolution and chemogenomics

Chemogenetic characterization through in vitro evolution combined with whole-genome analysis can identify antimalarial drug targets and drug-resistance genes. We performed a genome analysis of 262 Plasmodium falciparum parasites resistant to 37 diverse compounds. We found 159 gene amplifications and 148 nonsynonymous changes in 83 genes associated with drug-resistance acquisition, where gene amplifications contributed to one-third of resistance acquisition events. Beyond confirming previously identified multidrug-resistance mechanisms, we discovered hitherto unrecognized drug target–inhibitor pairs, including thymidylate synthase and a benzoquinazolinone, farnesyltransferase and a pyrimidinedione, and a dipeptidylpeptidase and an arylurea. This exploration of the P. falciparum resistome and druggable genome will likely guide drug discovery and structural biology efforts, while also advancing our understanding of resistance mechanisms available to the malaria parasite.Bill and Melinda Gates FoundationThe National Institutes of HealthThe National Institute of Allergy and Infectious DiseasesThe National Institute of General Medical SciencesDepto. de Bioquímica y Biología MolecularFac. de FarmaciaTRUEpu