  We construct a new type of locally homeomorphic quasiregular mappings in the
3-sphere and discuss their relation to the M.A.Lavrentiev problem, the Zorich
map with an essential singularity at infinity, the Fatou's problem and a
quasiregular analogue of domains of holomorphy in complex analysis. The
construction of such mappings comes from our construction of non-trivial
compact 4-dimensional cobordisms $M$ with symmetric boundary components and
whose interiors have complete 4-dimensional real hyperbolic structures. Such
locally homeomorphic quasiregular mappings are defined in the 3-sphere $S^3$ as
mappings equivariant with the standard conformal action of uniform hyperbolic
3-lattices $\Gamma$ in the unit 3-ball and its complement in $S^3$ and with its
discrete representation $G=\rho(\Gamma)$ in the group of isometries of $H^4 $.
Here $G$ is the fundamental group of our non-trivial hyperbolic 4-cobordism
$M=(H^4\cup\Omega(G))/G$ and the kernel of the homomorphism $\rho \!:\!
\Gamma\rightarrow G$ is a free group $F_3$ on three generators.
