We have isolated cDNA clones encoding human apolipoprotein (apo) A-I. Twenty putative apo A-I cDNA clones were selected by screening 10,000 clones of an adult human liver cDNA library with an oligonucleotide probe. The probe was a mixture of synthetic 14-base-long DNA oligomers constructed to correspond to the codons for apo A-I amino acids 105-109. Four of these clones were examined further and showed 600-to 800-base-pair (bp) inserts. Preliminary restriction mapping and partial DNA sequence analysis indicated that the shorter inserts were a subset of the longer DNA inserts. DNA sequence analysis of the clone with an insert of -600 bp, designated pAl-113, revealed that it contained a DNA sequence corresponding to apo A-I amino acids 94-243. The DNA base sequence of this clone also contained a standard termination codon, polyadenylylation signal, and poly(A) tail. Partial DNA sequence ofa second clone that contained an 800-bp insert, designated pAI-107, showed that it corresponded to apo A-I amino acids 18-243 and also included the 3' untranslated region. Isolation of these cDNA clones will facilitate molecular analyses of apolipoproteins in normal and disease states.

It has recently been suggested that polymorphisms in the human apolipoprotein A-I (apo A-I) gene locus may be related to the development of premature atherosclerosis and hypertriglyceridaemia. To understand if and how these polymorphisms affect apo A-I gene expression, we studied the genomic sequences flanking the apo A-I gene. Here we show the presence of another apolipoprotein gene, apolipoprotein C-III (apo C-III), approximately 2.6 kilobases (kb) downstream of the 3' end of the apo A-I gene. We also show that the apo A-I and apo C-III genes are convergently transcribed and that a polymorphism previously reported to be associated with hypertriglyceridaemia may be due to a single base pair substitution in the 3'-noncoding region of apo C-III mRNA.

A cDNA library derived from human cerebral cortex was screened for the presence of sodium channel a subunit-specific clones. Ligton of three overlapping clones generated a full-length cDNA clone, HBA, that provided the complete nucleotide sequence coding for a protein of 2005 amino acids. The predicted structure suggests four homologous repeats and exhibits greatest homology and structural similarity to the rat brain sodium channel H. A second cDNA clone, HBB, that encodes a different subtype of sodium channel was isolated. Hybridization of DNA a nts from the 3' untranslated region of HBA and PCR with primers derived from HBB with human-hamster somatic cell hybrids loalie these clones to human chromosome 2. In situ hybridization to human metaphase chromosomes mapped the structural genes for both HBA and HBB sodium channels to chromosome 2q23-24.3. The sodium channe HBA gene product was expressed by transection in CHO cells. Expressed HBA currents were voltage-dependent, sodium-selective, and tetrodotoxinsensitive and, thus, exhibit the biophysical and pharmacological properties characteristic of sodium channels.Signaling in the brain is mediated by the activity of voltagegated and ligand-gated ion channels. Sodium channels, archetypes of the multimember family of voltage-gated channels, are responsible for the rising phase of action potentials in electrically excitable cells (1) and have been extensively studied in a variety of cells, including human neurons (1, 2). Sodium channels vary in subunit composition and complexity (1,3,4). In rat brain, the channel complex consists of an a subunit ofMr -260,000 and two nonidentical p subunits ofMr -39,000 and 37,000 (3, 4). The a subunit is sufficient to form a functional channel, as demonstrated by heterologous expression of cDNAs (3-6); the role of the smaller subunits is not yet understood.Sodium channels are the targets of a variety of clinically valuable drugs, such as local anesthetics, anticonvulsants, or antiarrhythmics, and of various toxins (1, 4). However, little is known about the molecular structure and specific pharmacology of human brain channels, goals hitherto hampered by the limited accessibility of the tissue to experimental manipulation. Availability of cDNA clones for these proteins and their expression in heterologous systems would provide powerful tools to investigate their fundamental structure and pharmacological properties and to assess efficacy of therapeutic intervention. Localization of sodium channel genes to human chromosomes is an important step in exploring their involvement in the etiology of heritable neuropsychiatric disorders that have been mapped and in developing molecular markers for clinical screening programs (7).We report here the complete amino acid sequence of the a subunit of a human brain sodium channel,1 its localization to human chromosome 2q23-24.3, and its expression from cDNA in CHO cells. A preliminary account ofthis report was presented elsewhere (8). MATERIALS AND METHODSIsolion of cDNA Clones. Standard mol...

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