The idea of the communication failure between Gregor and his family is emphasized through the use of a very powerful metaphor, i.e. The doors in Gregor's room. Gregor's room is both a safe retreat and a place of complete isolation from his family, similarly to how the author himself took refuge from his father in his room. In fact, Gregor's room can be deconstructed as a symbol for Kafka's own life in his father's house; in this sense, the room becomes an escape in both cases. In Gregor's case, the room symbolizes his escape in both instances of his life; as a young man, he retreats to his room where he is at the same time hidden from and harassed by his family. Secondly, as a bug, he finds shelter in his room which also acts as his prison as he is no longer able to exit without his family's help. The author's inability to communicate and his uneasy relationship with his father are replicated in the story of Gregor's transformation. The doors of the room are a symbol of Gregor's status within his own family: he is their prisoner. His room has three doors, one for every family member to knock on; here the doors are seen as a means of controlling his life. They all order him to wake up and go to work; in fact this is the only kind of communication between Gregor and his family from which he is in fact, isolated although they all live under the same roof. The issue of communication is very strong throughout the story. Gregor becomes detached from humanity not only through the physical process of...

The failure to communicate with his own family creates a breach between Gregor's inner life which has essentially remained the same, and the outer world which perceives him as an insect, and not a human being. In other words, Gregor remains Gregor in his own eyes, but his appearance determined his sister and parents to regard him as a mere insect. This accounts for the communication wedge between the now-insect Gregor and his family who do not accept that despite his appearance, he is still their son and brother. With the exception of the rare loving addresses of his mother, Gregor is shown neither affection nor understanding.
No explanation is provided as to Gregor's metamorphosis. In fact, such an explanation would is not even relevant but the reader is free to assume that the salesman turned into a giant bug because of the hardship and isolation of his life. However the main change in his life is brought by his helplessness and his feeling of redundancy in the eyes of his own family. His personal life does not change dramatically as he is shown the same lack of compassion and understanding as before. Nevertheless, he is now completely unimportant to his family as he can no longer provide for them hence they sever all ties with him and stop seeing Gregor as a member of the family.

Kafka, Franz. The Metamorphosis. Kessinger Publishing, 2001.