You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Sino-Tibetan_relations_during_the_Ming_dynasty

Context:
The Ming dynasty granted titles to lamas of schools such as the Karmapa Kargyu, but the latter had previously declined Mongol invitations to receive titles. When the Ming Yongle Emperor invited Je Tsongkhapa (1357–1419), founder of the Gelug school, to come to the Ming court and pay tribute, the latter declined. Wang and Nyima write that this was due to old age and physical weakness, and also because of efforts being made to build three major monasteries. Chen Qingying states that Tsongkhapa wrote a letter to decline the Emperor's invitation, and in this reply, Tsongkhapa wrote:

Question:
Who was the founder of the Gelug school?

Je Tsongkhapa