Johann Christian was a German Kantor. He studied at the Thomasschule in Leipzig from 1727 to 1733, and enrolled at University of Leipzig in 1733. J.S. Bach wrote in a report from 1730: “not yet ready to be used in the 1st choir (figural music)”. After his studies he became Kantor in Brena and later in Mutzschen.
Source: fine-print footnotes in the Bach-Dokumente