Stearoyl-CoA Desaturase 4 Gene

Abstract

The cloning of a fourth mouse SCD gene, mSCD4, as well as its corresponding cDNA and amino acid sequences are disclosed. Mouse SCD4 is expressed mainly in the heart tissue and synthesizes the bulk of monounsaturated fatty acids in the heart. The disclosure here enables new tools (e.g., nucleic acids, polypeptides, antibodies, vectors, recombinant cells, and transgenic and knock-out animals) for studying the function of various SCD isoforms and their connection to various disease conditions. New tools for converting saturated fatty acyl-CoA to monounsaturated acyl-CoA and for identifying SCD modulators including isoform-specific modulators are also enabled. In addition, given that accumulation of lipid in the heart (fatty heart) can have deleterious consequences, the present invention also provides a new prevention and treatment target for fatty heart as well as methods for screening candidate drugs.

1 . An isolated nucleic acid comprising an uninterrupted nucleotide coding sequence or its complement wherein the uninterrupted coding sequence encodes an amino acid sequence selected from SEQ ID NO:2, an amino acid sequence that is at least 90% identical to SEQ ID NO:2, or SEQ ID NO:2 with one or more conservative substitutions. 
     
     
         2 . The isolated nucleic acid of  claim 1 , wherein the uninterrupted coding sequence encodes an amino acid sequence that is at least 95% identical to SEQ ID NO:2. 
     
     
         3 . The isolated nucleic acid of  claim 2 , wherein the uninterrupted coding sequence encodes an amino acid sequence defined by SEQ ID NO:2. 
     
     
         4 . The isolated nucleic acid of  claim 3 , wherein the uninterrupted coding sequence is defined by nucleotides 167 to 1225 of SEQ ID NO:1. 
     
     
         5 . The isolated nucleic acid of  claim 1 , wherein the nucleic acid consists of an uninterrupted nucleotide coding sequence or its complement wherein the uninterrupted coding sequence encodes an amino acid sequence defined SEQ ID NO:2. 
     
     
         6 . An isolated nucleic acid comprising a nucleotide sequence or its complement wherein the nucleotide sequence is at least 90% identical to the uninterrupted nucleotide coding sequence of  claim 5 . 
     
     
         7 . A vector comprising the nucleic acid of  claim 1  operably linked to a non-native promoter. 
     
     
         8 . A cell comprising the nucleic acid of  claim 1  operably linked to a non-native promoter. 
     
     
         9 . A transgenic animal comprising the nucleic acid of  claim 1  operably linked to a non-native promoter. 
     
     
         10 . A genetically engineered mouse cell in which the mouse SCD4 nucleic acid sequence has been disrupted. 
     
     
         11 . A mouse heart cell in which its SCD4 activity is inactivated. 
     
     
         12 . A mouse that lacks expression of functional SCD4 protein. 
     
     
         13 . The mouse of  claim 12 , wherein the mouse SCD4 nucleic acid sequence has been disrupted. 
     
     
         14 . An isolated polypeptide comprising an amino acid sequence selected from SEQ ID NO:2, an amino acid sequence that is at least 90% identical to SEQ ID NO:2, or SEQ ID NO:2 with one or more conservative substitutions. 
     
     
         15 . The isolated polypeptide of  claim 14 , wherein the polypeptide consists of an amino acid sequence selected from SEQ ID NO:2, an amino acid sequence that is at least 90% identical to SEQ ID NO:2, or SEQ ID NO:2 with one or more conservative substitutions. 
     
     
         16 . The isolated polypeptide of  claim 14 , wherein the polypeptide comprises an amino acid sequence that is at least 95% identical to SEQ ID NO:2. 
     
     
         17 . The isolated polypeptide of  claim 14 , wherein the polypeptide comprises an amino acid sequence defined by SEQ ID NO:2. 
     
     
         18 . An antibody that specifically binds to the polypeptide of  claim 15 . 
     
     
         19 . The antibody of  claim 18 , wherein the antibody specifically binds to a polypeptide that consists of an amino acid sequence defined by SEQ ID NO:2. 
     
     
         20 . A method for identifying an agent that can modulate an enzymatic activity of mouse stearoyl-CoA desaturase 4 (SCD4), the method comprising the steps of:
 providing a preparation that contains a polypeptide comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:2 and displays a mouse SCD4 enzymatic activity;   contacting the preparation with a test agent;   measuring the SCD4 enzymatic activity and comparing the activity to that of a control preparation that is not exposed to the test agent wherein a higher or lower than control activity indicates that the agent can modulate the enzymatic activity of mouse SCD4.   
     
     
         21 . The method of  claim 20 , wherein the preparation is a microsomal preparation. 
     
     
         22 . The method of  claim 21 , wherein the microsomal preparation is derived from cells that are genetically engineered to express the polypeptide comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:2. 
     
     
         23 . A method for identifying an agent that can modulate the expression of mouse SCD4, the method comprising the steps of:
 providing a cell that expresses SCD4;   exposing the cell a test agent;   measuring SCD4 expression level in the cell and comparing the level to that of a control cell that is not exposed to the test agent wherein a higher or lower than control level of expression indicates that the agent can modulate the expression of mouse SCD4.   
     
     
         24 . A method for identifying an agent that may modulate SCD4 activity, the method comprising the step of:
 providing a polypeptide according to  claim 14 ;   exposing the polypeptide to a test agent; and   determining whether the agent binds to the polypeptide, wherein a binding indicates that the agent is likely to be able to modulate SCD4 activity.   
     
     
         25 . The method of  claim 24 , wherein the polypeptide of  claim 15  is provided. 
     
     
         26 . A method for identifying an agent that can modulate SCD4 biological activity comprising the steps of:
 administering a test agent to a mouse; and   determining the effect of the agent on the SCD4 biological activity in the heart tissue.   
     
     
         27 . The method of  claim 26 , wherein the SCD4 biological activity is measured indirectly by the level of monounsaturated fatty acids, triglycerides, or both in the heart tissue. 
     
     
         28 . A method for converting a saturated fatty acyl-CoA to its corresponding monounsaturated fatty acyl-CoA, the method comprising the step of:
 exposing the fatty acyl-CoA to mouse SCD4 under the conditions which allow the formation of the corresponding monounsaturated fatty acyl-CoA.   
     
     
         29 . The method of  claim 28 , wherein the saturated fatty acyl-CoA is palmitoyl-CoA or stearoyl-CoA. 
     
     
         30 . A method for preventing or treating fatty heart in a mouse comprising the step of:
 reducing SCD 4 activity in the heart cells of the mouse.