In elucidating functionally important single-stranded loop regions derived mainly from three models in genomic hepatitis delta virus (HDV) ribozyme possessing self-cleavage activity, we have constructed several internal deletion variants of the HDV133 molecule (654-786 nt on genomic RNA) by oligonucleotide-directed mutagenesis. When self-cleavage activities were compared among variants, the HDV133DI-1 (deletion of 701-718 nt) and HDV133DI-3 (deletion of 740-752 nt) ribozyme could maintain their self-cleavage activity, despite at reduced level. However, the activity could be regained in both mutants by some extent under partially denaturing conditions. These results suggest that the above two single-stranded RNA loop regions in HDV ribozyme are not part of the catalytic core but might be involved in the stability of the molecule. In contrast, deletion mutants such as HDV133DI-2 (deletion of 696-722 nt), HDV88DI-1 (deletion of 701-718 nt), HDV88DI-2 (deletion of 696-722 nt), and HDV88DI-4 (deletion of 733-760 nt) abolished catalytic activity. These results suggest that the remaining single-stranded regions of bases between 726-731 and 762-766 in the HDV88 ribozyme may be the potential regions to interact with Mg2+ ions.
Abstract. Achondroplasia is the most common skeletal dysplasia and is caused by defective fibroblast growth factor receptor (FGFR) 3 in endochondral chondrocytes. Children with achondroplasia may have high cervical myelopathy due to stenosis of the craniocervical junction and an increased risk of sudden death. We report a female patient with achondroplasia who required surgical decompression at the age of 13 mo. The female patient was diagnosed with achondroplasia clinically, radiologically and genetically shortly after birth. The newborn period was uneventful. She developed head control at the age of 6 mo, but she could not sit by the age of 12 mo. At the age of 8 mo, her parents noticed her eyes did not close and a diagnosis of left peripheral nerve palsy was made. Occasional hyperextension of the trunk was observed. There was also minimal asymmetry of voluntary leg movement and bilateral ankle clonus. By these findings craniocervical junction compression was strongly suspected. MRI examination revealed compression at the craniocervical junction by the occipital bone and myleomalacia. The patient underwent suboccipital decompressive surgery at the age of 13 mo. Recovery after surgery was uneventful, and although her left facial nerve palsy did not improve, gross motor function had improved by the age of 2 yr. The patient is now cognitive and neurologically normal at the age of 3 yr. Infants with achondroplasia are at risk of lethal sequelae of craniocervical junction abnormalities, so careful neurological assessment and early MRI examination is recommended.
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