Mongoose and node js - TypeError: object is not a function

The issue that it doesnt let me use the genre schema i have 2 schemas user and genre user schema works fine but the genre schema is undefind

user.js - schema

var mongoose = require('mongoose');
var Schema = mongoose.Schema;

var Genre = require('../Models/genre');

// create a schema
var userSchema = new Schema({
  name: { type: String, required: true, unique: true },
  email: { type: String, required: true, unique: true },
  password: { type: String, required: true },
  age: String,
  gender: String,
  genres: [Genre.genreSchema]
});

// the schema is useless so far
// we need to create a model using it
var User = mongoose.model('User', userSchema);

// make this available to our users in our Node applications
module.exports = User;

genre.js - schema

var mongoose = require('mongoose');
var Schema = mongoose.Schema;

// create a schema
var genreSchema = new Schema({
  name: { type: String, required: true, unique: true },
  age: String,
  gender: String
});

// the schema is useless so far
// we need to create a model using it
var Genre = mongoose.model('Genre', genreSchema);

// make this available to our genres in our Node applications
module.exports = Genre;

genre controller - router --- same as user router controller

var express = require('express');
var bodyParser = require('body-parser');
var Genre = require('../Models/genre');

// ROUTES FOR OUR API
// =============================================================================
var router = express.Router();              // get an instance of the express Router

// middleware to use for all requests
router.use(function(req, res, next) {
    // do logging
    console.log('Something is happening.');
    next(); // make sure we go to the next routes and don't stop here
});

router.route('/genres')

    // create a genre
    .post(function(req, res) {
        console.log(Genre);

        **//here is the error when trying to post new genre**
        var Genre = new Genre(req.body);      // create a new instance of the user model

        // save the genre and check for errors
        Genre.save(function(err) {
            if (err)
                res.send(err);

            res.json({ message: 'Genre created!' });
        });

    })

    // get all the genres 
    .get(function(req, res) {
        Genre.find(function(err, genres) {
            if (err)
                res.send(err);

            res.json(genres);
        });
    });

    module.exports = router;

server.js - the app js

var express = require('express');
var app = express();
var bodyParser = require('body-parser');
var userRouter = require('./Controllers/user');
var genreRouter = require('./Controllers/genre');

var mongoose   = require('mongoose');
mongoose.connect('mongodb://localhost:27017'); // connect to our datababase

// configure app to use bodyParser()
// this will let us get the data from a POST
app.use(bodyParser.urlencoded({ extended: true }));
app.use(bodyParser.json());

var port = process.env.PORT || 8080;        // set our port


// REGISTER OUR ROUTES -------------------------------
// all of our routes will be prefixed with /api
app.use('/api', userRouter);
app.use('/api', genreRouter);

// START THE SERVER
// =============================================================================
app.listen(port);
console.log('see whats happening on port ' + port);

why the model is undefind only when i post new genre? and for user it works fine? is it the way to do schema whithin schema? or there is a better way?

i have try to use only the genre model with out the user and it still same error

i hope i am clear enough thanks for the helpers