Yes, GLIA is a Scrabble word!

Letter values in Scrabble US: G 2, L 1, I 1, A 1.

Is it a valid word?

GLIA is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

sustentacular tissue that surrounds and supports neurons in the central nervous system; glial and neural cells together compose the tissue of the central nervous system