The Supreme Court has issued notice on plea seeking direction to the CBI to file status report in disproportionate assets case against Mulayam Singh, his sons Akhilesh and Prateek Yadav. The case dates back to 2007. "We want to know what has happened to this case? There is a status report of 2007. What has happened? We would like to know whether the case is registered?" the apex court quizzed the CBI.