Molecular defects associated with antithrombin deficiency and dilated cardiomyopathy in a Japanese patient.

OBJECTIVE: The molecular basis for the antithrombin (AT) deficiency and dilated cardiomyopathy (DCM) combined in a Japanese patient was investigated. METHODS: We analyzed candidate genes -SERPINC1 for AT deficiency, and TNNT2 and LMNA for DCM. In addition, we examined the characteristics of recombinant mutant AT and evaluated the LMNA mutation associated with DCM by molecular modeling. RESULTS: Genome sequencing of SERPINC1 revealed a C-to-A transversion in exon 6 that resulted in a p.Pro439Thr mutation of AT, which was previously reported as a pleiotropic effect type II AT deficiency (AT Budapest5). However, expression experiments with recombinant 439Thr-AT showed normal heparin affinity, slightly reduced secretion, and low specific activity, which suggested that this mutation exhibits an intermediate feature of type I and type II AT deficiencies. In a survey of gene abnormalities causing DCM, we found no causative gene defect in TNNT2; however, we identified a G-to-C transversion in LMNA that resulted in a novel p.Asp357His mutation in lamin A/C. This acidic-to-basic residue substitution might have impaired the head-to-tail association of two lamin dimers leading to DCM. Further, we identified both SERPINC1 and LMNA mutations in the patient's daughter and son, both of whom had AT deficiency. These data suggested that a p.Pro439Thr mutation in SERPINC1 and a p.Asp357His mutation in LMNA might have cosegregated in this family, associated with AT deficiency and DCM, respectively. CONCLUSIONS: We identified missense mutations in SERPINC1 and LMNA genes to be associated with AT deficiency and DCM, respectively, which might have cosegregated in the family of the patient.

Molecular basis of antithrombin deficiency in four Japanese patients with antithrombin gene abnormalities including two novel mutations.

We analyzed the antithrombin (AT) gene in four unrelated Japanese patients with an AT deficiency, and individually identified four distinct mutations in the heterozygous state. There were two novel mutations, 2417delT leading to a frameshift with a premature termination at amino acid -3 (FS-3Stop) and C2640T resulting in a missense mutation (Ala59Val). Previously reported mutations, T5342C (Ser116Pro) and T72C (Met-32Thr), were also found in the other two patients. To understand the molecular basis responsible for the AT deficiency in these patients, in vitro expression experiments were performed using HEK293 cells transfected with either wild type or respective mutant AT expression vector. We found that -3Stop-AT and -32Thr-AT were not secreted into the culture media, whereas 116Pro-AT and 59Val-AT were secreted normally. We further studied the heparin cofactor activity and the binding to heparin of each recombinant AT molecule. Ser116Pro mutation significantly impaired the binding affinity to heparin resulting in a reduced heparin cofactor activity. In contrast, we found that Ala59Val mutant AT unexpectedly showed a normal affinity to heparin, but severely impaired the heparin cofactor activity. Our findings suggested that FS-3Stop and Met-32Thr mutations are responsible for type I AT deficiency, whereas Ser116Pro and Ala59Val mutations contribute to type II AT deficiency, confirming that there were diverse molecular mechanisms of AT deficiency depend upon discrete AT gene abnormalities as reported previously.

Fos-enkephalin signaling in the rat medial vestibular nucleus facilitates vestibular compensation.

In the present study, we first observed up-regulation in preproenkephalin (PPE)-like immunoreactivity (-LIR), a precursor of Met- and Leu-enkephalin, in the rat ipsilateral medial vestibular nucleus (ipsi-MVN) after unilateral labyrinthectomy (UL). By means of double-staining immunohistochemistry with PPE and Fos, a putative regulator of PPE gene expression, we revealed that some of these PPE-LIR neurons were also Fos immunopositive. The time course of decay of these double-stained neurons was quite parallel to that of UL-induced behavioral deficits. This suggests that these double-labeled neurons could have something to do with development of vestibular compensation. We next examined correlation between Fos and PPE expression in the ipsi-MVN by means of a 15-min pre-UL application of antisense oligonucleotide probes against c-fos mRNA into the ipsi-MVN. Gel shift assay and Western blotting revealed that elimination of Fos expression significantly reduced both AP-1 DNA binding activity and PPE expression in the ipsi-MVN after UL. C-fos antisense study also revealed that depression of Fos-PPE signaling in the ipsi-MVN caused significantly more severe behavioral deficits during vestibular compensation. Furthermore, studies with PPE antisense and naloxone, an opioid receptor antagonist, demonstrated that specific depression of enkephalinergic effects in the ipsi-MVN significantly delayed vestibular compensation. All these findings suggest that, immediately after UL, Fos induced in some of the ipsi-MVN neurons could regulate consequent PPE expression via the AP-1 activation and facilitate the restoration of balance between bilateral MVN activities via the opioid receptor activation, resulting in progress of vestibular compensation.

Intracranial vertebral artery dissection mimicking acute peripheral vertigo.

When diagnosing and treating patients with acute vertigo, the clinician must differentiate brain lesions from benign peripheral disorders. We here report a rare case of acute vertigo caused by intracranial vertebral artery dissection mimicking peripheral disease. A 67-year-old man presented with spontaneous nystagmus and moderate ataxia preceded by neck pain. No other neurological signs were observed, suggesting acute peripheral vertigo. However, magnetic resonance imaging (MRI) demonstrated a cerebellar infarction. Simultaneous magnetic resonance angiography (MRA) showed no flow void of the left vertebral artery and contrast-enhanced MRA demonstrated a double lumen sign, suggesting that vertebral artery dissection was a cause of infarction. The clinical course was favorable without anticoagulation drugs, which are sometimes contraindicated because of the potential risk of subarachnoid hemorrhage. Vertebral artery dissection can cause cerebellar infarction in patients without vascular risk factors mimicking acute peripheral vertigo. Careful history regarding the neck pain is important and MRA in combination with MRI can replace angiography in diagnosing this disorder.

Cavernous haemangioma of the internal auditory canal: a case report.

We report a patient with a cavernous haemangioma of the internal auditory canal (IAC). A 47-year-old man presented with a left profound hearing loss and a left facial palsy that had progressed over 5 years. With a preoperative diagnosis of acoustic or facial nerve neurinoma, the tumour was removed totally by a translabyrinthine approach. Intraoperatively, the tumour appeared red; it compressed the facial and cochlear nerves, and adhered to the vestibular nerve. The tumour was diagnosed as a cavernous haemangioma upon histologic and immunohistochemical examination. No recurrence of tumour occurred, but hearing loss and left facial palsy persisted. Although cavernous haemangiomas of the IAC is found in small size less than 10 mm, they often cause severe hearing loss and facial palsy. Our patient had no improvement of facial palsy, but many reports describe recovery of facial nerve function.