UserName field with uppercase value

hi,
in my registration form u have username field with unique username validation.
the problem is when in registration form the user type “Myname” as username cause the first character “M” is uppercase in account page user cannot update any field like FirstName-LAstName-Email or … the error says : Your username is invalid
because username in account page is uppercase : “Myname” but user profile page is root/user/myname with lowercase “M”.

i think registration form have to save plain and lowercase version of username value inside database.

but how can i make it happen?!

Thanks.