EXCLUSIVE : When Canadian director Leah Nelson and producer Lauren Miller Rogen first read Sarah Leavitt’s graphic memoir  Tangles : A Story About Alzheimer’s, My Mother and Me,  it was a subject matter that hit home in a very real way.  The story, which is the basis for Nelson’s animated feature debut  Tangles  that is world premiering as a Special Screening on Thursday (May 14) in Cannes , follows Sarah, who has to leave her exciting life as an activist and artist in 1990s San Francisco to return to her eccentric family in the conservative small town she recently fled when she learns that Alzheimer’s is beginning to erase her mother Midge’s vibrant personality.  The bittersweet and poignant film, which is also playing In Competition at Annecy next month, features a stellar voice cast including Julia Louis-Dreyfus, Bryan Cranston, Seth Rogen , Samira Wiley and Beanie Feldstein with Abbi Jacobson voicing the lead role of Sarah. Charades is shopping international rights to…