1. A DNA segment comprising a regulatory sequence and a heterologous nucleic acid molecule that is to be expressed and which originates from a different genetic context than said regulatory sequence, the heterologous nucleotide sequence being operatively linked to said regulatory sequence, said regulatory sequence being selected from the group consisting of: (a) regulatory sequences comprising the nucleotide sequence shown in SEQ ID NO: 1, as shown in SEQ ID NO: 2, as shown in SEQ ID NO: 3 or as shown in SEQ ID NO: 4; (b) regulatory sequences comprising the nucleotide sequence contained in the insertion of clone DSM 15111 and obtainable by amplification using two oligonucleotides having the sequences indicated under SEQ ID NO: 9 and SEQ ID NO: 10; (c) regulatory sequences comprising at least one nucleotide sequence of SEQ ID NO: 1 from position 1166 to 1746, from position 1166 to 2049, from position 1785 to 1843 or from position 1953 to 2775; (d) regulatory sequences comprising at least one nucleotide sequence of SEQ ID NO: 2 from position 529 to 1079, from position 529 to 1390, from position 1118 to 1175 or from position 1291 to 2137; (e) regulatory sequences comprising a nucleotide sequence which is at least 75% identical to a sequence as defined in (a) to (d) or which comprises a nucleotide sequence which is at least 78% identical to the nucleotide sequence as shown in SEQ ID NO: 1 from position 1166 to 1746 or from position 1166 to 2049 or to the nucleotide sequence shown in SEQ ID NO: 2 from position 529 to 1079 or from position 529 to 1390, which comprises a nucleotide sequence which is at least 82% identical to the nucleotide sequence as shown in SEQ ID NO: 1 from position 1785 to 1843 or to the nucleotide sequence as shown in SEQ ID NO: 2 from position 1118 to 1175 or which comprises a nucleotide sequence which is at least 75% identical to the nucleotide sequence as shown in SEQ ID NO: 1 from position 1953 to 2775 or to the nucleotide sequence as shown in SEQ ID NO: 2 from position 1291 to 2137; and (f) regulatory sequences comprising a nucleotide sequence which hybridizes under stringent conditions with a complementary strand of the regulatory sequence as defined in (a) to (e) and which provides early, transient expression of a heterologous nucleotide sequence in proliferative neuronal determined cells.