Hyperhomocysteinemia, a risk factor for vascular disease, injures endothelial cells through undefined mechanisms. We previously identified several homocysteineresponsive genes in cultured human vascular endothelial cells, including the endoplasmic reticulum (ER)-resident molecular chaperone GRP78/BiP. Here, we demonstrate that homocysteine induces the ER stress response and leads to the expression of a novel protein, Herp, containing a ubiquitin-like domain at the N terminus. mRNA expression of Herp was strongly upregulated by inducers of ER stress, including mercaptoethanol, tunicamycin, A23187, and thapsigargin. The ER stress-dependent induction of Herp was also observed at the protein level. Immunochemical analyses using Herpspecific antibodies indicated that Herp is a 54-kDa, membrane-associated ER protein. Herp is the first integral membrane protein regulated by the ER stress response pathway. Both the N and C termini face the cytoplasmic side of the ER; this membrane topology makes it unlikely that Herp acts as a molecular chaperone for proteins in the ER, in contrast to GRP78 and other ER stress-responsive proteins. Herp may, therefore, play an unknown role in the cellular survival response to stress.

Mutations in the EPM2A gene encoding a dual-specificity phosphatase (laforin) cause Lafora disease (LD), a progressive and invariably fatal epilepsy with periodic acid-Schiff-positive (PAS+) cytoplasmic inclusions (Lafora bodies) in the central nervous system. To study the pathology of LD and the functions of laforin, we disrupted the Epm2a gene in mice. At two months of age, homozygous null mutants developed widespread degeneration of neurons, most of which occurred in the absence of Lafora bodies. Dying neurons characteristically exhibit swelling in the endoplasmic reticulum, Golgi networks and mitochondria in the absence of apoptotic bodies or fragmentation of DNA. As Lafora bodies become more prominent at 4-12 months, organelles and nuclei are disrupted. The Lafora bodies, present both in neuronal and non-neural tissues, are positive for ubiquitin and advanced glycation end-products only in neurons, suggesting different pathological consequence for Lafora inclusions in neuronal tissues. Neuronal degeneration and Lafora inclusion bodies predate the onset of impaired behavioral responses, ataxia, spontaneous myoclonic seizures and EEG epileptiform activity. Our results suggest that LD is a primary neurodegenerative disorder that may utilize a non-apoptotic mechanism of cell death.

Acad. Sci. USA (97, 13913-13918; First Published November 28, 2000; 10.1073͞pnas.250478897), the authors note that the exponents of some entries in Table 1 were misprinted. The correct values appear below. www.pnas.org͞cgi͞doi͞10.1073͞pnas.191384698 STATISTICS, GENETICS. For the article ''Significance analysis of microarrays applied to the ionizing radiation response'' by Virginia Goss Tusher, Robert Tibshirani, and Gilbert Chu, which appeared in number 9, April 24, 2001, of Proc. Natl. Acad. Sci. USA (98, 5116-5121; First Published April 17, 2001; 10.1073͞pnas.091062498), the authors note the following: ''In our discussion of the pairwise fold change method on page 5118, we cited a paper by Ly et al., crediting them for the method. We did not mean to imply that it was deficient for the analysis of their experiments. In fact, Ly et al. incorporate (98,(6384)(6385)(6386)(6387)(6388)(6389), the authors wish to correct the position given for the amino acid that was mutated in the patient. The mutation ''R187W'' should be ''R188W. '' www.pnas.org͞cgi͞doi͞10.1073͞pnas.191390798 FEB2, 19p; FEB3, and FEB4,. A small population of individuals with FS has additional generalized epilepsy (1) or afebrile seizures. Genes for a ␤-subunit (␤1) and an ␣ I -subunit (Na v 1.1: SCN1A) (10) of the neuronal voltage-gated Na ϩ channel have been identified to be responsible for generalized epilepsy with febrile seizures plus (GEFSϩ) type 1 and 2, respectively (11, 12). However, a large number of patients with GEFSϩ still show no mutation for those genes. These, therefore, suggest that other genes might also be involved in GEFSϩ and FS associated with afebrile seizures. The chromosomal locus 2q24, in which GEFSϩ has been mapped, harbors not only Na v 1.1 but also other ␣-subunits including Na v 1.2 (SCN2A) (10,(13)(14)(15). Given that Na v 1.2 is also expressed in high levels in the central nervous system with a tissue-specific profile (16), Na v 1.2 is an intriguing candidate. In the present study, we report a mutation of Na v 1.2 found in a patient with FS and afebrile seizures. A channel harboring the mutation shows abnormal electrophysiological properties that may underlie the neuronal hyperexcitability that triggers seizure activity. Materials and MethodsPatients and Pedigrees. This study recruited nineteen unrelated Japanese families with members clinically diagnosed with GEFSϩ or febrile seizures associated with afebrile seizures. Each participating subject or a responsible adult signed an informed consent form approved by the Ethics Review Committee of Fukuoka University or similar committees of the participating institutions. The proband of family K1 is a 6-yr-old boy with normal development (Fig. 1A). He had the first febrile seizure (FS) at 8 months of age and suffered 17 episodes of FS thereafter at both high and low grade fever. The FS were generalized tonic or tonic-clonic convulsions with duration of 1-5 min per episode. Since 4 yr of age, he also has experienced brief afebrile atonic seizures 5 times. The...